Can’t orgasm

I’ve been with the same guy for 2 1/2 years. I’m obsessed with him and the sex is great and everything feels right. I love love love having sex with him. But I’ve never been able to have an orgasm. For a long time it wasn’t bothering me but it really bothers him that I can’t do it or he thinks he can’t give it to me. (He is the only guy I’ve ever had sex with). And I don’t know what to do, I’ve never orgasmed before so I don’t even know where to start?!?! Help plz.