OK, so if Diogenes' (researcher, not doctor) theory is correct - and I think a lot of us believe it is - absolutely nothing is happening to your thyroid. It has nothing to do with your thyroid.
The immune system produces different antibodies for everything it attacks. So, all auto-immune diseases have their own antibody. The anti thyroid antibody you had tested was the TPOab, which only attacks the thyroid (put simply).
But, there's another type of antibody that affects the TSH, and gives false results when the TSH is tested. So, those high results you had were false, and nothing to do with your thyroid. And nothing to do with how much levo you were taking. Just a 'mistake' - you could say - in the labs because of the TSH antibodies. You don't have to understand the difference, just accept that there are lots of different antibodies that do lots of different things.
Now, above, Helvella has explained, in simple term, what has to be done to check on those antibodies. But, it shouldn't be down to you to find the lab to do the tests, that's what you have a doctor and an endo for. That's their job. Did you even tell your doctor about the TSH antibodies?
And, the most important point of course, is that antibodies fluctuate. I'm sure you must have read that before. So, they were high for three of your tests, so that you got rediculously high readings, and your doctor panicked, and increased your levo by to much.
So, the next test you had, the antibodies were low, and didn't affect the test, and because of the high dose of levo, the TSH test showed over-medication (absolutely NOT hyper, you are not hyper, you are just over-medicated).
Your doctor has been extremely silly in all this. What he should have done before increasing your dose, was test your FT4 and FT3. And, if they had been in range, then it would have been obvious that there was something wrong with the TSH test. But, he didn't. Instead, he has sent you into a panic, and now you can't think straight. But, there's nothing to panic about. So, you've got to take a deep breath, and try to think about all this logically. The TSH isn't even a thyroid hormone. It is a pituitary hormone. And rarely reflects thyroid status.
The TSH is a deeply flawed way of deciding dosing. And this is just one more proof if proof were needed. Doctors have got to start looking at the Frees, or this is the sort of thing that happens!
So, do you understand better now? If it's still not clear, tell me.