Confused over current situation - need advice

Okay so, Hey, Im a 18 year old male who has officially ran out of places to turn to about this so now i'm looking to the help of the internet to help me. (This is long so please bare with me) So i have been with my girlfriend for nearly 3 years now and we have been constantly on and off, the reason for this is because she keeps making mistakes and i keep forgiving her but this time its too much. Before we started seeing each other i really liked her obviously being teenagers we hanged out a lot seen each other every day talked every night blah blah... it turned out her feelings were mutual however because i was to slow to the punch some other guy bet me to it and she started to see him for a little while, i unfortunately got in the way of them unintentionally and she ended up confessing her feelings for me, so she ended things with this guy and we started to see each other at first i was a little paranoid and jealous but mainly protective i really liked her and didn't want to loose her again at any cost. i am also a very prideful and protective person which in turn explains my reaction to some of the things i did. we had been going out for 3 months by this point and we started to hang out with one of my friends, i should probably also mention that her ex and past had fucked with her head and caused her to no want me to watch porn, masturbate, speak to other woman, go to partys and even go out with my friends, she even didn't like me watching any movie or tv show with any slightly attractive women in it such as for example the big bang theory. none of this bothered me too much as all i cared about was her and i knew her heart and mind were broken and i took it upon myself to fix her... This never happened. So my friend and girlfriend were kinda close before we got together and they got closer since which made me feel very uncomfortable and slightly angry, i had asked her not to have him round at her house when i wasn't their, she then had him round at her house twice after i asked this of her without telling me i found out from a friend, once i confronted her it never happened again but she facetimed him a couple of nights in a row until 4 in the morning. this really pushed me and i asked her not to contact him she then continued to contact him and followed by asking him to learn and perform a song for her she really like on guitar, an instrument which i played. at this point i couldnt handle anymore and shattered my friendship with him who i had been friends with for 14 years. A few incidents happened after this like guys trying to pull her, although she refused and pushed them away, it still sat with me a little, a year after the incident happened with my friend, she broke up with me because she didnt feel the same. we then got back a week later and everything was fine, another few things happened and then she heard her ex had been talking about their past sex life to people, i was at my aunts house and she said she was going to phone him and sort shit out i said thats fine dont be long she replied she'll be 5 mins tops. she was on the phone with him for what she said was 30 mins and never replied to my 20 phone calls and texts for an hour and a half to this day i dont know what was said, a week later she broke up with me and i asked if it was because of her ex she said no, a week later we met up to talk about things, she told me she met up with her ex the night we broke up, she said nothing happened they just talked i believed her despite my anger and despair we got back together. we were okay for a while then i started training at the gym, between that school and work it was taking up my life so i never had a lot of time for her, so she went to lunch with her friend her ex and his friend, once she got home and told me i was angry, angrier than i had ever been but yet again i was ready to forgive her until she said i dont regret it at which point i finished with her on the spot with tears coming out my eyes like a waterfall, we went a month and a half this time broken up before i decided to forgive her and take her back. this time everything was great no arguing no nagging from either of us and no shouting either, it got a couple months in a i got a gut feeling something was wrong so as relationships go an argument erupted out of nothing and she confessed she kissed her ex when we were split up for the month and a half, she kissed him around 5 days into the break up and told me it was planned to go further however it didn't. i had gained all my trust and love back for her and it was completely shattered again i didn't know how to act i wasnt angry or sad nothing i cried a little because it hurt and then i was emotionless. we broke up i took her home and that was it i still haven't forgiven her and she knows it however i gave her another chance. I realise i am a fool and an idiot, i keep making the same mistakes over and over again i cant believe a word that comes out her mouth and everytime we kiss hug or have sex i cant help but think about what she did and was planning on doing with her ex, i think about it everyday and my heart breaks everyday i cant breath when i think about it and i cant think either i just go almost numb with a pain in my chest. the only thing that keeps me with her is that i love her and i dont want to loose her i still feel like she makes my life better and i make her better even though thats not the case... Tonight her sister was with my friend they have a little love life of their own and being the little nosy thing she is went through his messages specifically the group chat that me and all my friends are in, at this point i was single and would never even dare to say something like this in a relationship however i just found out the woman i loved was going to fuck her ex while i sat their depressed, I had made a joke about going out with this girl that i used to know as she posted on facebook she wanted a 'Hot Boyfriend' im not that up my self that i would think of myself as hot so i made a joke that i would suit her (not in those words entirely but not far off) and then my friend who is an idiot added to the joke about if i got the chance it would be a threesome to which i responded yeah between me her and her sister, this was just guy banter i would never actually go through with it and it was all just a joke, so when my girlfriend found out she went crazy at me saying how insecure she felt and was almost comparing it to what she had done, as if it was just as bad we argued for an hour an came to a resolve but im done with all the fighting and the controlling, i just want to be in a happy relationship with someone who loves and cares for me as much as i do for them, i have never giving her any reason to make her want to do things she did everytime we talk about it she admits she doesnt know why she done them, I need advice on what to do next i love her to pieces i cant imagine life without her and the thought of loosing her breaks my heart even more, I have experienced series of emotional and physical pain i have been emotionally unstable but nothing compares to the feeling i get thinking about loosing her, because of everything she has put me through i dont care if i live or die and im reckless because of it and i feel as though im going to kill myself being reckless on day, i need to know what to do, has anyone been someplace similar to me and can offer advice? should i end things despite how much i dont want to? i really dont know what to do and will appreciate any help at all. Thank you for taking the time to read my problem.

Hey so I am a 20 yr old female. Believe it or not I've been in the same boat. I was in a relationship with this guy for 3 1/2 years off and on. Even though he treated me bad, he cheated on me with so many women, I still stayed. In my head I would be like yeah he does this and that to me but I know we can be happy bc I would over indulge on the happy memories we had at some point and dilute the bad times. I would always blame other ppl for him acting that way, I would say "oh that girl is an easy slut for flirting with him".. Even though the random girl wouldn't even know he had a girlfriend n he was the one who would start it. I was just so focus on everything ending with me being with him bc I didn't think I could ever find anyone else, no not anyone like him. And people would tell me to leave him that he was bad for me that I deserved better. But I now see that I myself thought I couldn't or that I didn't deserve better. Truth is doesn't matter what ppl tell Yu bc I've been there they use to tell me I was gonna find someone else bc he wasn't the one for me, n when we are blinded we don't wanna believe we are like yeah that happens to other ppl not us, this is different this is special, this will work out, but it won't. So sorry for the long reply but let me tell Yu no one can physically help Yu, no one can rip her out of your heart , only Yu can. And believe me when I say I know it's not easy it hurst so much! But at the end when that's over n Yu find someone else who actually treats Yu with respect then you'll think of how silly it was to try to stay with someone who was not meant to be with you.

it is better to be loved by someone than to love someone...you gave her many chances,you are not at fault...find someone worth your love....start thinking about yourself before you regret....you'll definitely find your real love.good luck