For myself, I've always found that having sex makes me want more sex. Fantasizing makes me want to fantasize more often. Masturbating makes me hornier all around. However, when you're not in the mood... it just kind of spirals downward from there sometimes.
And then there's the advice that any doctor would give you... get lots of sleep, eat the right foods, get good exercise, and look after yourself.
I know being raped may be part of the problem, but, I wanted to tell you that having a lower sex drive than your man is a very common relationship issue facing all kinds of women out there. It's not necessarily because of the past.
However, if you are having trouble with sexual thoughts because of the rape... maybe talking to a counsellor is a good idea if you haven't already. Or maybe just talking with your boyfriend about it would be good. Maybe keeping a journal if talking about it is too difficult? Maybe talking here is helping
I guess those are just my thoughts.. I hope it helped a tiny bit.