HELP ME WITH MY NERVES

Hi guys !

I am seeking help on trying to figure out what is going on with my body. I recently just missed my period 3 weeks ago, and my new period is coming up. I never have been late to my period and already took 3 pregnancy test to confirm I am not pregnant. I gained a couple of pounds but I’m going crazy why my period has not came yet. I am very nauseous when I eat and just been thinking and in my head. Has this happened to anybody? Can someone please give me advice?