4 days past expected AF

So .. still no sign of AF. Normally when AF comes .. I spot red the first day and have to use a tampon that night as it heavies quickly. I took a HPT 6/24 (came back negative) and 6/25 .. I started having a brown discharge only when I wipe. And it's very light .. didn't need a pantyliner overnight. My cycle is normally 28 days but if this isn't AF, I'm on day 33. So I'm not sure if I'm just testing too early or if something else is up. I can't get into my primary obgyn until August :(