Hi,
The first thing we want to rule out is whether or not you are pregnant,although there are many causes to missing periods but since you have history of thyroid and you have ruled that you can't be pregnant so i would recomend you to get a throid test.
When was the last time when you got your throid test and if you got them recently then please attach the reports.
There can be many more hormonal causes to it,and periods can be corrected by giving hormonal drugs which will cause withdrawl ble ...
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