Thanks for the info. I really don't know anything about it. Bit clueless really. I thought. It was an infertility problem.

I've had my tubes tied and not really something I was expecting. I doubt this is what the issue is though. When I go back after the us I might have the guts to mention the bum issue. I nearly did today but was worried she would want to look while I have my period.
So you went to the doctor but didn't tell her anything about it? What's the ultrasound for - if she thinks you have endo, an ultrasound will show nothing unless there is a endometrioma (endo cyst) on an ovary.
I know it's embarassing, but doctors are very used to dealing with this stuff (just watch embarassingbodies andyou'll feel better), just be honest and remember, a doctor can't make you do anything you aren't comfortable with.