Confused?

So normally my periods are regular, sometimes a few days late. So my period is due for the 3rd and i got in Dec 31, 3 days earlier. I showered and saw blood so i guess my period started. But it’s been super light today like there’s barely any blood and it’s just brown. I went to get up to go pee and i got dizzy and when i peed, a sharp shooting pain occurred in my stomach and now I’m feeling nauseous. Does anyone know what this means?