34th cycle day

Today is my 34th day in my cycle and I'm starting to wonder where my af is. Glow had originally predicted 9/14 but now it's not saying I'm due until 9/18. My cycles have been ranging from 28-35 days since I started using this app in January. I felt very sick to my stomach this morning and was in/out of the bathroom on the toilet. A couple bm later, I sort of felt better. Felt crampy but just a little bit different than what my period starting usually feels like. My cm is very heavy and creamy with barely a sticky feeling (sorry for the tmi)." Probably a 1% chance I would be pregnant but I'm wondering why my period is being unpredictable.