To soon or no?

AF was suppose to start yesterday. But never came and never had symptoms. Today there was a little blood so I put in a tampon. Went to change it and there was hardly anything. And it was brown. Then nothing for a while. But I’m another tampon because I was going somewhere and didn’t want to bleed through if I did start. Took it out later and barely nothing at but a little bit of brown again. I’ve also been feeling nauseous all week off and on. Any ideas what might be going on? Or what I need to do?