Notmyname, I created an account to mention this: my sister had nausea like you describe for 3 years. Doctors were stumped, but her bariatric surgeon figured out it was her gallbladder. She never had any pain or classic symptoms, just her nausea. Her bariatric surgeon removed it when he did her sleeve and she hasn't felt the nausea since. If you still have your gallbladder, you might consider having it checked since losing a lot of weight often causes issues.