Is it because I'm a big girl?

Alright, so I posted a bit ago about how my period was a week late and I had gotten brown spotting but all negative tests. I'm now 16 days late and still haven't gotten a positive test so I'm trying to face the fact that I'm not pregnant (again 😔) but I'm really worried about why I'm not starting my period and I can't see my gynecologist for awhile. I know that lots of things can push back a period but could I not be having a period because I'm fat? I don't really know what's going on with me but I'm a tad upset.