AF has switched twice!!

Al
Why has my week switched twice. Normally supposed to start last Friday(dec 5th). Then it switched to the 13th. Now it's saying the 10th.  I know I've posted a million times but it just changed. 
I've had two faint tests and my bbt has been high. I'm crampy, sick feeling, and my chest is a little sore. 
Idk if this is a sign or if my AF is late now. Why does it switch yet I still have these lines..and symptoms?