Day 324 since my last period

You read that correctly, almost a year since my last period. I made a post on here in April and she still hasn't arrived. I have talked to my doctor about it and got a ultrasound appointment scheduled but it got canceled due to covid. That was 2 months ago and I still haven't gotten it. Again no change in diet, lifestyle, mental health, and 100% not pregnant. I dont feel any different physically but who knows. What should I do? Should I be worried? I'm 16 if that makes any difference, but idk though.