Late period

Hi guys,

Im 13 (soon 14) and a virgin (obviously). I got my period in April of 2018. It hasn’t been regular or irregular. But while using this app (and another period tracking app) I found out that my period was late by 20 days. I kept having kind of medium to heavy discharge, until I saw some blood or something that reminded blood. It was mixed with the discharge. I’ve had it for about two to three days. I’m not sure what it is. Its light,so I don’t need to wear a pad or tampon. Is it spotting? A very light period? Should I be worried? Please help me. I’m scared something is wrong but I don’t want to go to the gynecologist or something.