AM I A VICTIM OF D******** OR AM I A TERRIBLE PERSON? WHAT SHOULD I DO PLEASE HELP ME

I have been dating my boyfriend for almost four years. I’ve cheated on him before, once because of alcohol which i addmitedly have a problem with, and second time because i was too nice to tell someone no right away. Just kissing though, and i told my boyfriend about it and expressed my deep regret and said NOTHING of the sort would EVER happen again.. A few months later i was invited to stay over at this girl who was my friend at the times house , who i knew had a crush on me. She offered me alcohol, against my better judement i accepted. Then, after a few drinks she offered me a bottle and said to drink it all but refused to have any. I did find this suspicious but because i am an alcoholic i drank it all gladly. Then, the next thing i know, we are calling over a guy who she had been having s** with who we both knew from school. They have both been asking me for a threeway since i met them… So if i had not been intoxicated i would never have been in such a situation. Now, i am straight so if he hadn’t been there perhaps nothing would have happened but i was deeply under the influence… I don’t remember making the decision to cheat, and going there i knew i NEVER wanted to do that again… I even recall being naked and physically fighting my female friend off of me and dont remember why..But the next thing i know i am naked chained to a bed. Now i am sure that i did an said things that provoked this… But i was completely unhappy with the situation imediately and couldn’t vocalize this feeling of disgust, or that i wanted it to stop and for them to stop touching me… When i awoke i immediately ran from the house ready to kill myself, completely hysterical. That day the so called friend of mine is no longer my friend. I told my boyfriend that i got drunk and had suspicions of being drugged and that i fought her off when she asked to have s** and went to bed but woke up next to them both with no clothes on… He belived me, but everytime i close my eyes i have flashbacks of what happened. I want to marry this boy, but is it possible i will never forget unless i tell him that i was partially to blame? Am i partially to blame? Am i entirely to blame? If i am not entirely to blame then should i tell him the truth after havin partially lied already? Please help me:( i cannot be alone or close my eyes to sleep without having flashbacks and uncontrollably crying .