Period MIA for 80 days

Alright so I’ve always had abnormal periods but I feel like maybe I should see a doc to find out for the best. My last period was Nov 7-11 and before that Jul 30-Aug-3. I’m 19 if that helps, but before I see a doc I wanna know if anyone has an idea on what it could be? I’ve been stress free, no job at home most times, diet has been the same and no sex so any ideas?