Can't orgasm.... What can I do?

Okay, this is a really embarrassing question and even though I'm on an anonymous site it still feels awkward asking. I have been dating my girlfriend for a little over a year now. She has a bit of a problem when it comes to our sex life. We haven't slept together yet (we've had oral and hand sex), but she can't get me to orgasm and this really upsets her. I don't really care, but it breaks down her self esteem (she is a little overweight, but she is starting to workout and losing the pounds fast). I've never had an orgasm, not from her, myself, or anything else. This is not something I want to go to a doctor about and not something I can talk to anyone about. I'm a 15 year old boy if this has anything to do with anything. When we mess around, it feels good, and there are moments where there is some extreme pleasure, but I never get off. I tried doing it myself but couldn't. Is there anything I can do to fix this....?