Gemma,

Are they testing your DH as well?

If they find nothing wrong with your hormone levels and you ovulate every month, then perhaps you would go in for a laparoscopy (to check for Endo) and a hysteroscopy (or whatever it is called where they check your tubes).

If you are getting pain and the ultrasound shows nothing, it is certainly worth getting a laparoscopy done to check out in more detail what that pain might be from - sometimes things don't show on an ultrasound but they find them during a laparoscopy.

Hope this helps!