Why Is T3T4 Low Again When It Was Rising Before?

Question: Hi there, I attached my latest labwork. I'm on 50 mcg Levothyroxine for 11 weeks, and my labwork is horrible. My story started with 5.66 TSH in April, 2020. T3T4 was within normal range back then, and I had vidamin D insufficiency. Doctor prescribed me vitamin D and 75 mcg Levothyroxine. At the 6 weeks checkup on 05/28/20, TSH down to 0.421, vitamin D back to normal, T3T4 not checked. Doctor told me to continue to take the 75 mcg. After taking 75 mcg Levothyroxine for 3 months, I had hyperthyroidism (on 07/31/20 TSH 0.01, Free T4 2.0). So doctor reduced the dosage to 25 mcg. Next blood test on 9/9/20 shows hypothyroidism with TSH 11.61, Free T4 low. Changed dosage to 50 mcg Levothyroxine. 10/05/20 TSH 58.51, Free T4 back to low-end average. 10/20/20 test, TSH goes down to 36.3, Free.T4,.Free.T3 goes back to normal. Continued 50 mcg dosage,.TSH continues to go down TSH 13.69, but Free T4 below normal again,.vitamin D deficiency again,.TPO antibody (checked.for the first time) crazy high. What is going on? Is vitamin D deficiency a factor? Do I have cancer or problem with my pituitary gland or is this just the good old Hashimoto? Is it Hashimoto for sure? Vitamin D deficiency couldn't cause this havoc? If 75 mcg too high, 25 too low, why 50 mcg doesn't work either? Should I start taking 75 mcg again? Or just keep taking 50 mcg for the time being as my TSH keeps going down and Free T4 is low because my body is trying to figure out how much hormone I really do need? What's happening with the free T4 level? Why is it low again when it was rising before? Is it vitamin D deficiency or tpo antibody? Thanks for your reply in advance.

But then why did I have hyperthyroidism after taking 75 mcg the first time? In July my TSH was 0.01 and Free T4 2.0. Is it not possible that because of the overdosing, my body stopped producing the hormone and then we should have gradually reduce the dose,, not dramatically and suddenly to 25 mcg? I mean after receiving too much supplemented hormone then not.recei ing basically any didn't just caused further damage b/c my body doesn't know how to react? With Hashimoto, rapid decline is common? I mean for 39 years nothing and then 1/2 year ago 75 mcg too much but now, that's the right dosage? Also, can anything else influence the TPO antibody count or it's Hashimoto only? Like allergy, Covid19, etc... Thanks.