Is this weird? Help!

Tessa
My boyfriend & I have been together for 2 years. We have also been having sex for these 2 years & he's the only one I've had sex w/. Sex is great, amazing actually!!! But I for some reason can't orgasm... Sometimes I get this feeling like it's a really good feeling & it feels like I'm going to but I can't. Why can't I? Is something wrong?