Help my brain? cycle help?

I'm in the tww of my second month ttc. I mentally kept track of the days my period started in the past and knew to expect it pretty much like clockwork 28 days later. I avoided having sex when my cervical mucus was fertile, and have successfully avoided pregnancy for two years with that method.  Now, paying extreme close attention and checking my cervix daily, I happened to notice the smallest spot of blood on the day my last period was due, again the following day, and I didn't full on bleed out until what would have been two days late. I had my period, and immediately went right into fertile CM the day it ended. Cycle days 8, 9, and 10 were egcm days and I made sure to have sex 2 times during that time and again on the first day that ewcm disappeared.