I think it takes a lot of courage to begin talking about the rape. It took a great deal for you talk to your boyfriend about what happened, including the fact that you needed to be under the influence. My guess is this kind of information may be difficult for him to assimilate. He simply may not know what to do or say, and may have a wide variety of reactions and feelings to sort through.
Your natural instinct to write this down and ask for help is probably the best thing you can do. In fact, I’m going to encourage you to do some expressive writing around this. Research has shown that it may be helpful to write about difficult events in our lives. Please write down your feelings about being stuck and not being able to talk to your boyfriend about this. If you have a journal this would be the place to put these thoughts and feelings. If you don’t already have a journal or diary, this may be the time to start.
Finally, I am encouraging you to talk to the people at your university counseling center. They are highly trained and can guide you from there.