Orgasm-less sex.

I'm 18 years old and have had 6 sexual partners in total and I've never been able to have an orgasm during sex. I can make myself do it just fine, but when it comes to having sex, it just doesn't happen. 3 of the 6 sexual partners were amazing and I always seem to get close, but never reach it.
 I'm currently sleeping with someone regularly (at least once a week for 3 weeks now) and the sex is amazing and I come very close to reaching an orgasm but it still doesn't happen. 
What can I do to help myself reach an orgasm whilst doing it? I'm sure I'm not the only one with this problem. It's just really frustrating when you have a close bond with someone and they can't make you cum. 
I don't believe it's his fault because I've only ever had an orgasm with another person whilst dry humping.
Please help.