I could use a little help!?

Desiree

My AF was due on the 16th according to glow. When that didn't happen it moved back to the 18th. Then that didn't happen it moved to the 20th. We took a couple of tests but we didnt see anything. Then on the 22nd I started spotting and my stomach was cramping so much and I don't cramp at all. Before this happened my AF was always on time ALWAYS. Now I can't get the glow app to update my period and everything is way off. Even my AF is very different. I have an appointment with my doctor on the 28th for a blood test for pregnancy. Has this happened to anyone else?