It never hurts to talk to a counselor about things that are bothering us. It also sounds like you were pretty careful with the condom, a good thing, but perhaps you should also be sure your girlfriend is on the Pill or has an IUD so you don't also cause an unwanted pregnancy. It doesn't sound like you have exposed yourself to an STD.
Anyway, seek out a good counselor, it will help you with general anxiety and intimacy issues.