I hate myself for ruining my relationship

Im going to try and make this as short as I possibly can: I'd been with my boyfriend for 2 years but before the summer of this year, things started changing. He became quite distant and I didn't feel he was putting much into the relationship anymore. It almost seemed he was having second thoughts, but every time I asked him about it, he would turn around and say everything was fine, that he would try harder and put in more effort. Anyway, nothing really changed. In the space of 2 years I had only been invited to his once, but had never met his family. I heard a lot about them and knew he was very close to his sister, but I never got the chance to actually meet them. He would have his friends over from time to time, but never me. (I'm 19 and he's 20 by the way) Every time we went out i was always paying for our meals as he wasn't doing so well with money (being at uni and that), i always bought him spontaneous gifts and gave him my everything, and for a while it just felt like all he was doing was take take take. Anyway, further into the summer one of my best friends could see i was a bit down in the dumps with the whole thing, so she invited me out with this big group of guys she had been friends with for some time. They were all between the ages of 21-23. It was a regular thing for her to go out with these guys every Friday, whether it was to the pub or out in town, and soon enough i became quite friendly with this bunch and would join them on the odd friday or weekends, with my best friend. A few weeks into this, my boyfriend turned around and told me that one of the guys in this group had actually been the guy his ex girlfriend had cheated on him with. Obviously I was quite shocked about this, but the problem was, this guy (we'll call him matt) was my best friends closest friend within the group, and i had actually taken quite a liking to him due to similar interests and him coming across very decent. At the news my boyfriend told me he would never stop me being friends with anyone, but to watch out for him. Anyway, time went on and i ended up becoming a lot better friends with this guy. I think the more my boyfriend pushed me away, the closer i became to matt because i wanted to make up for what was missing. It was nice having someone to talk to that actually took an interest. But within this whole time, i never ever developed feelings for him. I loved my boyfriend way too much, in fact a lot of people would call me 'whipped' because i would literally drop everything for him on the word go. So this guy simply became no more than a close friend. However, my boyfriend started to get jealous and upset with what i was doing and i started to see it and realised myself how awful i'd been. I had been doing what he did to me. I was pushing him away for another guy, and even though he knew the conversations were never flirty and he knew i didnt like him in that way one bit, its never nice to feel like you're losing someone to another man, especially when this guy lost him his first love. My boyfriend essentially hated him. He would always say, hes bad news, stay the hell away from him. As if things werent already bad enough, i now felt terrible for what i was doing. After speaking to my boyfriend, i tried digging myself out of this hole i had created in this close friendship with matt, but instead of 'going up' and getting myself out, i seemed to dig side routes to try and find a way out. Essentially, i knew i couldnt just cut off the friendship because that would also be a bad move, but my best friend had also informed me that matt now really wanted to be with me, so i panicked. He'd already taken my boyfriends first girlfriend away from him. Anyway, one night matt had a house party and me and my best friend went. I got a little too drunk and started telling random people about my relationship and how much i loved my boyfriend and was stuck in this situation. Matt took me away and told me he didnt want me saying things id regret in the morning. Anyway, him, me, my best friend and a few other girls all started drinking more and more. I dont remember this night very well but other sources told me i had been throwing up all over myself. Matt took me upstairs to where his only bathroom is, and i was leaning over the toilet for quite some time, until he took me into his room and sat me on the end of his bed with a glass of water. Regardless of how drunk i was, and how much sick was down my coat (gross i know), i decided to try and have a talk with him and sort things out. I told him i loved my boyfriend and what i had been doing was very wrong. I told him how much id enjoyed his company and how nice the friendship had been but it needed to tone down, because i was hurting my boyfriend and it wasnt fair on him at all. Matt was upset about this and got angry. He started telling me that he knew i loved him, in which i said i didnt. He then started moving his face towards mine and trying to kiss me. I kept saying no matt you cant do that, you're drunk and youre being stupid. He then grabbed me and pushed me down onto the mattress and started to kiss me. I was edging my face away and trying to not let his lips touch mine but hes a lot heavier than me so it wasnt really working. The only thing i thought to do was hit him as hard as i could in the balls, in which i did. He jumped off with and yelled 'what the fuck', i ran as fast as i could down the stairs and grabbed my best friend and pulled her out the house to get a cab home. After this happened i didnt tell my boyfriend was a month because i was so ashamed and i knew he would turn around and say 'i told you so'. The only person i told was my best friend and my mum, who told me i had to be very careful in making sure my boyfriend knew the truth in that i didnt cheat. I felt so disgusted in myself and for a long time i felt like i had cheated, because all though the kiss wasnt my choice and he took advantage of me when i was most vulnerable, the build up to it happening was and i should have listened to my boyfriend from the start. I was so scared and knew i was going to lose him. I finally rang him and told him when matt started leaving me abusive messages about how i had 'used' him. Anyway, long story short, my boyfriend broke up with me. Its been about 3 months since the incident and weve managed to get things back on track. Were seeing eachother again and i think hes comes to terms with what happened, and accepted it a little better. Although he probably still thinks i did cheat. I dont really blame him though. I had many people telling me i should have reported matt for what he did because it was against my will and i had to hit him to get him off me, but i just wanted to leave it alone to be honest. Anyway, things are slow but were working on growing back as a couple. Im so happy that were trying to make things work again but i cant help but hate myself all the time. I hate myself for hurting my boyfriend so much, and i cant imagine how he must be feeling. How can i learn to accept it and not blame myself so much?