I would have to agree with Ev. First stop the hand-jobs and let yourself get excited and worked up for your girlfriend. Many men complain that condoms decrease their sensitivity and I tend to think that is true. Sometimes you just have to experiment with different condoms (lubed, ribbed, ect...)to see which works best for you. On the other hand, some men actually like using condoms because it does keep them from going off too soon.(kind of reduces the over-stimulation) Anyway, I think that you should do some experiments on your own before you see a sexologist or any other professional. You are young and healthy and will find your own way. Good luck to you!