Advise please

Just come back from hospital. Thought I was having a consultation  but it  was for hysteroscooy I was annoyed I was nit told but I thought I am here now so just have it done.

the doctor said the lining is 14 thick  that's why it needs done.

she could nit get the instruments in it was extremely painful , I have quite a high pain thread hold  but had to tell her to stop.

she said I will have to have it done under GA  which I was surprised can they nit do it under mild sedation like you have for a colonoscopy 

sorry to sound stupid all this is because when having a ultra sound if stonach  the radiologist had to do as TV USED  and found thickening  any advise please would be greatly received thanks