ttc had a strange period cycle

ok, i started using the app when i recently had nexplanon removed (march 14th) started my period a few days later, watched my charting, had a normal for me period, did the bd often when i was ovulating amd even after. I was due to start af today the April 12th but i took a test the morning of the 9th and bfn and started spotting a couple hours later that day. then the 10th i had steady flow of dark red and brown blood. usually af is a solid 5 days but yesterday and today light, brown period discharge amd tgis evening virtually nothing only some super light spotting. so...my question is WTF? anyone have a similar experience?