Just because you have certain thoughts doesn't mean you have to act on them. If fears about liming guys is bothering you, then you certainly don't have to dump your gf and get with a guy to see. I find other girls attractive, but that doesn't mean I have to cheat on my wife to see if I want something else.

Try to take a deep breath and realize these things are just thoughts. You have control over your choices. If you have a problem with anxiety then maybe therapy or medications will help you find some relief.

Just enjoy your time with her and let things develope.