Period help

I am 23 years old and have NOT had my period for 18 months. I have seen a gyno and she put me on thyroid medication and told me to wait it out. It has been several months but still no period. I plan to go back next month just curious if anyone has any insight.

I am definitely not pregnant. I have always had inconsistencies but nothing like this. The longest stretch was 6 months. I am afraid I will never be able to have kids.

Has anyone else had this problem?