can't orgasm?

I'm 18 and I've never been able to orgasm. When I was in my earlier teens I never masturbated or anything so it was never really a goal but now I've been sexually active since April so it's become more of a priority. I can't give my boyfriend direction despite how hard he tries because I don't know how to have an orgasm on my own. I've been trying it on my own now and when me and my boyfriend are having sex but it gets to the point where my whole body is tense and I feel stressed and it's too much sensation so I stop. I don't immediately because I think I'm close but then nothing happens so I just give up. What's going on?