hello there.
I hope you are taking the medicine prescribed by your doctor for
thyroid.
because if you are, the weight will gradually decrease you don't have to worry much. but apart from that you could try the following.
1. green tea twice a day.
2. drink lots of fluids.
3. take 5 small meals a day.
4. brisk walking upto half an hour a day.
all the very best.