Your Endo, like most other doctors, fail to understand/accept that taking thyroid med in only one of two doses in 24 hours is very different from the continuous low flow of thyroid hormone from the gland in the untreated state. Thyroid med spikes FT4 and FT3 levels during the first 4 hours after ingestion, and causes the TSH to be suppressed for most of the day. A suppressed TSH when taking a significant dose of thyroid med does not mean hyperthyroidism, or over-medication, unless there are hyper symptoms due to excessive levels of FT4and FT3. It is illogical to conclude tht you are over-medicated when your FT4 of 12 is at the bottom of the range, and your FT3 of 3.5 is only 11% of its range.
From your symptoms and your FT4 and FT3 levels you are in need of an increase in your med dosages, not a decrease. You may never convince your doctor, but that is the case. In addition it is very important that your Vitamin D is at least 50 ng/ml, B12 in the upper part of its range, and ferritin should be at least 100. If not tested for those you should do so and then supplement as needed to optimize.
If there is any possibility of changing your doctor's mind, I have some info that might help with that. First, click on my name and then scroll down and read at least the Overview of a full paper on Diagnosis and Treatment of Hypothyroidism: A Patient's Perspective. Also, I am sending you a PM, with other info. To access, click on your name and then from your personal page, click on messages.
Sorry, I see there is some kind of error message when I try to send a PM. I'll try to get it fixed and then try again.
Vitamin D 65 nmol/L (50 - 75 suboptimal) I was taking 3000IU for a year but he wants me to retake prescription 800IU
Folate 4.29 ug/L (2.50 - 19.50) folic acid 5mg
Ferritin 23 ug/L (15 - 150)
B12 1193 pg/L (190 - 900) checked in October 2019, was taking B12 injections for low B12 symptoms, haven’t had any injections since February due to COVID
I would cut back on the D3 to 2000 IU daily. That should keep you above 50, which is adequate. 800 would not be enough. Your B12 is higher than needed. Can you take B12 as a supplement, instead of shots? Your ferritin is way too low. It needs to be at least 100. Low ferritin will cause a number of symptoms, some of which can mimic hypothyroidism. Following are reported symptoms of low ferritin:
faster heart rate
loss of sex drive
Pagophagia, or the compulsive eating of ice
numbness or tingling of extremities
sores at corner of mouth