I've never had an orgasm. :(

I've never had an orgasm! I'm 22. With a 1 1/2 yr old son. And a very fufilling sex life (other than that) we've tried diff positions, lube, anything that comes to mind but my body is just not having it. Don't get me wrong we have good sex, but it's starting to make him feel bad that he can't make me finish. Help :(