Does Bio identical hormone replacement therapy cause weight gain? I have packed on 20 pounds and feel swollen and bloated most of the time. If I stop taking the HRT what happens to my body?

Anything synthetic can put weight on.
It is not good to go off medicine without a doctors. Supervision. Make an appointment and discuss your options. Then if you are not satisfied check with an alternative meds. dr. that can help you make a safe transition from the HRT
To natural supplements.

I would find another doctor who specializes in bio-identical hormones for a second opinion on your treatment. Not all doctors are properly trained in HRT. My wife went to 4 different doctors before she found one who did thorough testing to determine the proper levels needed. She hasn't gained any weight whatsoever and totally got rid of her hot flashes. Plus, got her sex drive back. If you have a compounding pharmacy in your city, ask the pharmist for names of some of the doctors they work with.