I think the issue here is you get too sensitive before you climax to allow yourself to fully get off...... pretty much the only solution I can think of is to bite your lip and try to hold back...
My girlfriend is kind of like this, when she climaxes from oral sex, she almost immediately pushes my face away once she cums... it's way too sensitive for me to keep up my tongue barrage...
if you don't think you can keep your hands still... I might suggest trying handcuffs, just keep in mind you will squirm and scream in ultimate torturous pleasure if you do this as you will be relinquishing control of your orgasms to your partner, but I think you'll count it among one of the more intense sexual experiences you've had.
Also keep in mind there's more than one way to induce orgasm, clitoral and g-spot being the two primary ones, my g/f primarily climaxes due to penetration but I've heard this is rare..... find what makes you get off, you could try a different technique.... toys or whatever.... let us know if you need some more ideas.