Missed period &a Negative pregnancy tests

Alright ladies I need some opinions. Before anyone comments, I already made a doctors appointment for the 24th of July but I am anxious and want to hear if anyone else has gone through this. My periods are always around the same day every month (if I'm supposed to start on the 5th, I'll start somewhere between the 3rd and 7th). I was supposed to start my period last Friday. I am now a week late. A few days ago I was having severe anxiety that made me nauseous so I decided to take a test, negative. I've taken a few since then and they have all been Negative. PLEASE do not tell me my period is late due to stress. I know my body. I am not stressed, and there is no other lifestyle explanation to why my period is so late. Anyone had this experience?