and besides if your girl doesnt love you for you, and will want to leave you because of a possible physical condition, then.. she doesnt really love you man.
But i agree, your so nervous about performing right that anxiety is makin ya flaccid.
Its kinda like peeing at a public urinal, for some reason another you get "stage fright" and ya cant go. Im sure your physically ok, your just under stress from all thats being done and your worrying about performing.
If she leaves you for that, well thats her fault, not yours. She doesnt love you as much as she says she does.