The elusive Orgasm

I've never been able to orgasm with a sexual partner. I can when I masterbate (on my stomach with clothes on). I've been with my current partner for over a year and 1/2, and he is a GREAT lover and I truly enjoy sex with him. I enjoy it when he goes down on me, but it still doesn't "get me there". Whenever he tries to rub my clit with his hand, it's like too much stimulation with direct contact and it is wildly uncomfortable.  Anyone else have this issue? Any solutions or advice? Thanks!