I identify so much with this. I was also raped as a teen (at 15). I was at a party with friends, and (as always) we were all drinking to get drunk, if that makes sense. These "friends" laughed about it because they thought I was, like you, finally losing my virginity. Well, I suppose I was, but not in a way that
anyone would ever want. I didn't lose it, it was stolen. I had the same thoughts as you: that it was my fault, that I didn't fight back, that even though I said "no" I should have done more, that it wouldn't have happened if I wasn't so drunk...these things don't matter. What does matter is that I (and you) said no; we were ignored. A few months after the rape, a couple (true) friends convinced me to report it; I found out that this same guy had raped 3 or 4 other girls, all younger than I had been. The RCC (Rape Crisis Center) counselor I had was awesome. She told me that even if I had said yes, the fact that I was drunk meant that I was unable to consent; that constitutes rape. It might seem obvious, but that was my "wow" moment: it clicked. I saw it for what it was: devious and malicious rape.
I sincerely hope that you can believe these things about your own situation: it was NOT your fault, it WAS rape, and it WAS (very) wrong. Good luck with telling your therapist--I'm positive that she/he will be very supportive about this (if he/she isn't, find a different one lol!).
if okay. If you need someone to talk to, I'm here...Very sorry you had to go through this!