Hopefully you haven't fixated on this issue the past seventeen years! Sometimes it's fun to just enjoy the ride, but I can see where never being able to orgasm no matter what would get immensely frustrating. It could be something related to your physiological make-up that is causing this or it could be an inability to just completely let go and get out of your head during sexual endeavors because of stress, self consciousness, or other reasons. However, if you want to know, you could probably talk this over with your gynecologist to find out why.
I'd definitely say that you need to speak to a doctor and be examined. It could be something medically going on that is causing this.