Negative test but missed period

I dont know if this is something that happens to woman but i missed my period and then started bleeding 3days before my next period and i was bleeding for a few hours not heavy to fill a pad, it turned light pink then it was on and off then it turned brown an then it was gone, i dont think its my period because it lasted 2 days, if anyone experienced the same thing it would be helpful to know whats going on thankss