I just found out I'm Hypothyroid. My TSH levels were extremely high 149 and I have a goiter. I started on 150 mg of generic synthroid last week and had really started to feel better. I switched to 150 of brand Synthroid two days ago and I am feeling like **** again (very tired, irritable, not sleeping well, brain fog, feeling like I'm choking). How long until I feel better and will I continue to have good days and bd until my levels go down (the Dr. wants me at TSH 2)?