T3 and T4 can be "normal" but still not good enough. Were those Free T3 and Free T4 or were they Totals?
Do you know if you have Hashimoto's?
My T3 and T4 levels are remaining in the normal range. When I first got diagnosed three months ago, my TSH was 36. 4 weeks ago it was at 7.
Yes, it's possible. I did much better on generic levo than I did on synthroid. We're all different and we react differently to fillers/binders used to make the pills.
Also, in your case, it's not unusual for symptoms to return, worsen or for new ones to appear, when changing med or dosage. It's just your body adapting to the new med/dosage. It takes approximately 4-6 weeks for the new med/dosage to take full effect, then your body still has to "get well".
Do you have current thyroid labs, that you can post, so we can better assess your situation? As long as your med/dosage is being actively adjusted, you should be getting tested every 5-6 weeks for TSH, Free T3 and Free T4.
Do you know if you have Hashimoto's?