Being hypothyroid, you should have gained weight because your metabolism should be slowing down, fat mostly.
Still, if your medication consists of T4 (thyroxine) in the regimen, you should basically feel the brunt of the lack of medication 5 weeks from the day you stopped taking it. T4 having an half-life of about 1 week and medication generally take 5 half-lives to clear, so by now 3 to 4 weeks after you will soon be nearing your original hypothyroid levels.
If you had been taking too much medication then you might have ''wasted'' the food, but considering you've done the opposite, it would make little sense (even if one considers the beneficial effects of normal thyroid levels on protein turn-over) to blame this on the lack of medication.
Hell, you are lucky not to have packed on fat.