What is happening to me? Help me understand!

Hello. This is going to take a while to explain. But I need to talk to someone because this hurts so much and I'm confused. I started a new job around a year ago and I met a guy (David) at work that seemed really friendly. Before I continue, just wanted to say that I've been with my boyfriend Mike for 4 years now but we've been doing the "long distance" thing for months now. I love him very much and he is PERFECT. BUT..let me continue...so at first when I met David, he didn't tell me that he had a gf (long distance as well)..as we got to know eachother more and more, he told me that he was with this girl for years and then they broke up and this year they started going out again. David used to call me everyday after work to chat about anything..I would find his calls a bit weird and I would wonder what this guy actually wanted from me. I mean he kept on texting me everyday asking questions and he really seemed "interested" in me. And I was confused since I have a bf and he has a gf as well. We kept on talking everyday for months..and we even went out 3 or 4 times to hang out and have dinner (he was the one to suggest going out)..at that time my bf was really busy with work and he didn't have time to talk to me..but David was always there..talking to me every single day..so i started to fall for David..and i made more time for David..and my feelings for Mike were fading away. Suddenly out of the blue one day while texting..David tells me that he is getting engaged to his current gf. I tried to hide how hurt i was by this "news" and acted surprised..while i was really jealous. I continued being David's friend and considering him as just another coworker..but I couldn't..we would talk and flirt, and even fight like we were in a relationship! but we weren't..and nothing physical ever happened between us...even if he admitted to wanting to kiss me as well..but David never made a move..and neither did I..I don't know if we were both lonely at that time so we just needed someone to talk to...but I mean..I really felt a strong connection with this guy..I mean just when he looks at me, I feel like the chemistry is so strong, like we are magnets. One day while texting eachother, i asked him "do you feel like there is something more than friendship going on between us or is it just all in my head?", he then answered "yes..it's not all in your head"..and we met up after this convo..and I was so angry..that I just told him that I can't be friends with him anymore because it hurts too much and because he is getting engaged and I have strong feelings for him. He then said that he "started to have feelings for me" but then "stopped them because he has a gf" and "i always saw you as a sister". After he had told me that..i felt really stupid and used..like i was some kind of teenage girl getting her heart broken all over again. We stopped talking for a while after that..ignoring eachother at work..like we didn't exist..then after a good month..of crying and making things worse with my bf..i finally admitted everything to my bf Mike..and told him everything about David..Mike was not thrilled about it..but like i said..nothing physical happened between us..so I told Mike i needed space...and when David found out that Mike knew..he went all nuts on me..he told me that I broke a strong relationship for nothing..and that i had done a very bad thing..(in a way i knew he was right..) but i felt like maybe if i backed off from my bf..maybe David would see that i really wanted to be with him and leave his gf as well..but that was just stupid. David ignored me EVEN MORE...and i was heartbroken, lonely and miserable for a whole month. But i didn't show David any sign of weakness..i would see him at work and say hi politely..i would not talk to him or text him when i felt bad..i fought through it..like a soldier..and after a month..i was starting to miss my bf Mike..(we were on a break but he never let go of me)..so I started to fix things with him instead..and then when i felt like i was getting over David..I talked to him because it was getting really awkward between us at work and in the hallways..so I told David that I felt like he was playing me this whole time..acting all interested in me and then letting me go as soon as he saw that I had feelings for him..everything he did from texting,calling,giving me prolonged eye contact, touching me slightly on my arm..that was all a game..and i told him that..i told him that he is just a player..and he played me..and i fell for him hard..but i also told him that im over it all..and that im back with my bf..and i wish him the best with his gf..and that im not interested anymore. I tried to fake smiles at work..and act like everything was ok..when deep inside..i felt like pure shit..so i decided to travel..and i went on holidays..i started to forget David..and I was with my bf all the time..i would kiss my bf..and think of kissing David..(i know thats really bad..but sometimes u can't control how u feel)..i went on holidays for 3 weeks..and by the third week..my feelings for Mike were getting stronger and stronger..but then i had to return to work..and during all that time (3 weeks) i hadn't talked to David!! not once! i totally ignored him...so when i got back to work after 3 weeks, i saw David again for the first time..and BOOM..my feelings for him rose up again..and im like wtf..why?!?!?!? (BTW..i have David as a friend on facebook and i posted all the pictures of my trip with my bf Mike and I had a really great time with my friends and it shows) as soon as i saw David again, HE started talking to me again, coming up to my desk and starting convos..texting me again several times a day..waiting for me to leave work so we can leave together..inviting me over for coffee..and when we talked..he would ask me about my bf Mike..about his work..our relationship..and I would always say positive things..He then told me that his relationship with his soon to be fiance was on the rocks for a while..and i was like "oh really..well i hope everything is better now.." and then he told me that he got cold feet about the engagement and my reaction was "no don't do anything stupid, u will regret it, you are lucky to have her"..and his face would always change when i told him stuff like that..i was acting like i didn't care about him at all and was encouraging him to fix his relationship..he hasn't stopped talking to me on whatsapp..he has been chatting me up several times a day..ive been acting like his friend..but not too friendly..and ive been updating pictures with my boyfriend Mike on Fb..so can you tell me what is going on right now? what is happening with this dude? is he just a player..? does he have any interest in me whatsoever? or is he just playing me around like a toy..? is he chasing me because i made myself unavailable to him? i know guys like the chase...but really?!!?!?! i mean the guy is getting engaged...and he seems like he loves his gf..then why is he trying to get my attention so badly..why is he always the one to talk to me first..and chat..and ask a zillion questions..please help me..my heart can't handle it anymore..i need to get rid of my feelings for him..i mean he still looks at me so intensely with his eyes..and he compliments me..he seems jealous when i talk about my bf..but i mean what's the point of all this? i don't understand..please some advice..some guidance..just something...to help me understand..

Well tbh, I think your going for an impossible. I mean I think you know what's best but your mind is taking over your heart. Not good at all... I've been in. Similar situation a while back.. I guess it was the attention that was making me so confused. My bf, now fiancé, is a great mean and sometimes I wonder what could have happened if I would have let go? So yeah again it's the attention you are enjoying not necessarily an actual chance at love. You're both happy with your partners so don't ruin it. Guys/men are stupid! They are never happy with what they have ! They aspire way to hu and ruin things on they're way there don't be one of those honey.