I suppose to start my period on Wednesday???????

But omg something came today! i was shopping , (didn't feel anything ) til i got home i went to pee and see brown on my underwear!! What ????? i been feeling nauseous and don't want to eat all day but no period symptoms????? i never got a period this early?? it's not even a period????? omg!!! Could i be pregnant ????? 😬😭😭 i always start on the 28th of every month.