I doubt theres anything wrong with you. You may just need to relax. For me it takes a great deal of concentrating sometimes so my guy gets me off....hes not bad or anything, as a matter of fact, hes wonderful and I enjoy every second with him....
or maybe give your gal some pointers. Tell her how you like it done....you obviously know what you like because you can do it yourself. Just ask her to do it a certain way, or if she does it in a way you really like, tell her to keep doing it that way.
I'm a girlie, and would rather my guy tell me how he likes it then not reach orgasm at all during our sessions. I want to please him just as much as he pleases me....and sometimes MORE...