Welcome to HCM.
In almost all cases, your thyroid
hormone levels will return to normal or below normal after radioactive iodine
treatment. This may take 8 to 12 weeks or longer.
So your symptoms might be due to settling down of your thyroid level.
test is ideal after at least 7th day of missing period.
Otherwise you can confirm it by blood hcg
level and usg.
I would suggest you to keep in touch with your doctor and inform him about your symptoms.