Sure you could go and try shagging men, but that would upset your girl (and maybe you!) An ex of mine had a similer thing going on but he told me that he could never come until he felt he knew the girl really well and was comfortable with her (we've been together for a while now and he's off 3 or 4 times a day) So maybe if you spend some getting to know your girl really well and know that she loves you anyway you'll hopefully feel less anxious and be able to fully immerse (scuse pun) yourself in the situation and get maximum results!

-Sorry if that's a very 'girly' answer, also try havin a good smoke b4, I know that helps alot of girls to come, Good luck!