We sometimes hear of people who gain
weight, hypo or hyper, and others who lose
weight whenever
thyroid hormones aren't right, but you're the first who gains when meds are increased and loses when decreased (that I know of), just the opposite of what you'd expect.
Sorry, I don't even have a suggestion for you of what could be causing this. This comment will bump you up to the top...maybe someone else has some ideas.