Advice, please !!

I’m 46 days late and on cycle day 83. Ive taken 3 pregnancy tests and all came back negative, but I’ve missed 2 periods now. Has this happened to anyone else ?? Does anyone know why ??? I didn’t get my first period until August 2019 (2 months before I turned 16). I’m also fairly underweight (my bmi is 16.6), but I have been my whole life, I haven’t experienced any significant weight loss recently I’ve just always been small. Im kinda concerned and I think I should see a doctor or gyno but my mom won’t take me because we don’t have a good relationship (she simply doesn’t care) and because of covid-19. Do I have any reason to panic??