Help! I can only have an orgasm once and then I'm done :(

I have been sexually active for about 9 years. In that 9 years I can count on one hand how many times I've had more than one orgasm during sex.

It's incredibly embarrassing. I orgasm and then I get so sensitive that it is too painful to go on. Then my SO usually can't finish. I feel horrible. He said he doesn't mind, but I don't believe him. What is wrong with me? Does this happen to anyone else? What can I do to change this?

Please help!