I was drugged and raped by 2 men last year at a party and have had problems with sex since then.
I used to be able to orgasm at the snap of a finger, and I've noticed that it is A LOT harder to orgasm after that incident. I would say every 10 times I have sex I will only cum twice. I don't think of the rape during sex, but I think it is a underlying subliminal thing that is always on my mind, and always will be.
I know it would be hard, but try to communicate what has happened to your boyfriend. This will let him know that he isn't doing anything wrong, and it will possibly bring you two closer. If possible see a therapist. Communication is key. If your holding all of this inside and not telling anyone, I find that you think about it more. I only told two people, my mother and my best friend. But I held back from saying anything for several months, and I found that I pondered on it more when I hadn't told anyone.
If at all possible, invest in some things that may make your sex life more interesting. Masturbation is key. I feel that the more I masturbate the more I will be able to "train" myself to be able to "cum on command" again. It will take time, but I'm certain that it will get better.
good luck, from someone going through the same thing.