AF is Late

Okay so I am 3 days late on my period. I normally have 25-28 day cycles. Well today maykes my 28th day and I have yet to start. I know you can go up to like 35 days but I have never done that. Well today I woke up sore in my lower back. I keep running to the bathroom thinking my period may have started but instead I am just super wet. Sorry may be TMI lol. Anyways I have never done this before even when I got pregnant with my son 7 years ago. OHHH by the way I always breakout bad when my period is like a week away and I have no breakout this month. I also took a PT and got a BFN....... So I am a little confused and am wondering what you all think.