Finishing

Okay ladies, whoever is out there, I don't really ever post on here. This is actually my very first post I think but I have to this time. When my boyfriend and I have sex I have trouble finishing and it's not that he's not doing his job cause he is and is amazing but it's just I can't finish. I just have trouble doing it. It's always been like this and I don't know what is going on. Opinions?