clit so sensitive it hurts?

I'm really frustrated because I haven't been able to orgasm with my boyfriend. I can orgasm by myself, but I normally use a vibrator through my underwear because I can be really sensitive. He knows exactly where my clit is and at the beginning it feels really good, but then at some point I start shaking and jerking uncontrollably and then my clit gets so sensitive it actually hurts and I have to ask him to stop. I really want to orgasm with him, but this keeps stopping us.... any advice?