Sometimes, you can't have an orgasm when you want one. It might be that you're used to masturbating or having sex in a certain way. Maybe you're with someone new now and you need time to get used to being with that person.

It might also be that you tried too hard to keep your erection. So you kind of missed the chance to “let go” and now you can't get there again. Drugs and alcohol can also make it harder for a guy to ejaculate.

Try talking to your partner about what feels good. That usually helps. If you're unable to ejaculate more than half of the time, talk to a doctor or health care professional. (For more info on finding one, click here.)