Just need some reassurance.

Hi all. I’ve had irregular periods since I was 12, I’m 18 now and it seems to have gotten worse. A couple months ago my cycle was 40 days long, and then dropped down to 29 days for two months, then back to 33 days. I’m now on say 36 of my current cycle and I was supposed to get my period 3 days ago (2 days according to another period tracker… I don’t know which one is more accurate.) I definitely know I’m not pregnant, but I’m unsure what could be holding up my period. Any advice to help de-stress? The holidays have been overwhelming, could that be why?