&gt; I'm happy to be "convinced" usually, but my boyfriend knows I have a difficult time saying no (because of cultural and psychological background). To me, it was clear that my disinterest was sufficient to indicate that I wasn't willing at all to negotiate.

Be careful with this.. because it sounds like you're putting the responsibility of your consent onto your boyfriend, because of your background. If that makes sense? He knows you have a difficult time saying no, so he should question every time you say yes? He shouldn't take your 'yes' as a yes unless..? It's his responsibility to determine when you've given consent or not. Even when you're not clear and giving the *opposite* indication. Even if you're willing and reciprocating? To him, it wasn't clear that you were disinterested so there was a dip in communication, and hence things progressed. To him you *were* willing to negotiate. You showed you were. If you don't say anything and then ultimately reciprocate, how is he to know?

Maybe you and he should sit down together and talk about what things and words really signal a definite 'No', and what signals a 'No, for the whole of tonight'. I also wouldn't go tossing the term 'sexual assault' around.. but it seems like you've already really alienated him.