Turned on=pain! Help :(

OK so this is really weird, it started about a year ago. One day when I got turned on I got this pain in my vagina if felt like a pulled muscle, but once I started to have sex it went away. This happens to me every time now.. I've gone to the gyno and she can't figure out what's wrong with me she wants to send my husband and I to a sex therapist.. I know I'm not crazy cause I can feel it! I joke around with my husband and say that I'm going to get blue bald if we don't have sex, but in all honesty it sucks because if we don't have sex right then and there I have to put up with the pain until it gos away. It sucks so bad I even cry sometimes because of the pain. So if this happens to any one else please help me out with what I can do.