Doctors know nothing about thyroid, but like to be seen to be doing something. So, they lower your dose! OK, I'm a cynic, but it really does seem to be that way. They like your TSH to be nice and high in range, because otherwise, you will 'tip over' into hyper! Which just goes to show how very little they know about thyroid!
If you are hypo, you cannot become hyper. The thyroid just doesn't work that way. You can, on the other hand, be over-medicated - but people usually aren't. And, just having a low TSH does not mean you are over-medicated, just that you are on thyroid hormone replacement. You are only over-medicated if your FT3 is over-range. But, they never even test that. So, how do they know? That's the question to ask.
Did you ask him why he thought you were 'hyper' (does he even know what 'hyper' means?)? Did you protest? If you just sit there and don't say anything, he takes that as consent. But, he isn't supposed to just reduce your levo willy-nilly, without consultation, first. The patient should give informed consent to changes in his medication. Your doctor is there to advise you, not dictate to you. Tell him how bad you feel since the reduction, and that you would like your original dose reinstated, please. If he starts wittering on about osteoporosis and heart attacks, just tell him you are willing to take the risk - because the risk is yours to take.