Do not take any calcium within 4 hours of taking your thyroid replacement. It interferes with absorption. You do not start thyroid replacement right after surgery because surgery can cause a release of thyroid hormone and you could be hyperthyroid if you added replacement then. Surgery itself, of any kind, is traumatic to your body and general anesthesia affects some people in odd ways, altho that wears off pretty fast. You could be suffering just from the aftereffects of the surgery itself. After all, you did just have your throat cut open! Be patient with yourself. Right now you have no idea if you are taking the correct amount of replacement and will not know that until your first TSH in a few weeks. This is hard to explain, but thyroid hormone has a half life of 7 days, meaning half of the first pill dose will still be in your system a week after taking it and will not be totally out of your system for a month. So this means the doses accumulate until they reach a steady state. 2 days is not enough to achieve this. You had an influx of thyroid because of surgery, just manipulating the gland, that dissipated over the postop week, probably leaving you a bit hypo before starting replacement. Now it may take a bit to catch up. But catch up you will.