I don't think that your dream necessarily reflects anything about your boyfriend. More likely the rape is symbolic of something in your life. Ultimately only you would be able to determine this.
There was a thread on this forum about rape dreams a few weeks ago...if you go back a page or two you might find it. I think it was Lori who initiated it. She was speculating that many women seem to have rape dreams. We didn't reach any conclusions but it was an interesting topic. I had a rape dream myself many years ago, but it seemed for me to be about issues of faith/spirituality. The dream didn't bother me, but felt very intense.
I think, most certainly for women, rape is a strong subject and is tied in with ideas about power, trust etc. etc.
You might think about the qualities in your boyfriend that stand out for you and see if there is anything in this. Often we dream about people because of what they symbolize in our own consciousness.
Maybe others on the forum will have more insight. Perhaps check out these previous threads to see if anything resonates: