What is happening with my cycle? and how do I make the app reflect it?

Ladies, my cycle was supposed to start on the 6 but it didn't. on the 8th I started a light spotting that goes between pink and brown. and I'm still just seeing that. this has happened before and a few days later I have gotten a regular cycle. I have no idea what that's about. The app won't let me adjust the period so it says I stated it on the 8th. By the time is gone i will have had a 2 week long period and my fertility week is showing to be right after the period ends. it also makes the date of my next cycle totally wrong. Has anyone else experienced something similar? I've taken several pregnancy tests and they are all negative. Thanks in advance!