Unexpected period after nearly 3 years of menopause

Hi, I'm new to this but worried about something and hoped you may be able to give me some sensible advice. I have been in the menopause for nearly 3 years after an ovary was removed as a large cyst had grown around it. Last week I had a total knee replacement and have been taking lots of drugs on top of my medication for bi-polar. Yesterday I had an extra pain like a period pain and started bleeding. I don't know what to do. I don't really want to be pulled around anymore by doctors as I'm in agony still and my head is spinning too! Sorry to bother you. Thanks