After Every Hashi Flare Up, I End Having To Urinate

After every hashi flare up, I end having to urinate a lot. Shortly after that stops, my symptoms start going away. However, I thought that frequent urination was a symptom of hypothyroidism. Why does it only happen when I start to feel better? And why, when my endo increases my dose, I gain weight? Shouldn't I be losing weight?