Aunt Flo is late❌‼️

Hey, can someone please tell me what's going on? I'm on pill, and my periods are usually on time but now I'm late 4 days ( but i had my last pill only 2 days ago)  and my last period was very weak ( mostly brown discharge with a little bit of blood). Is it possible that my birth control is the reason? Or what is??? 😩😱😭