On Jan.8-Jan.15 i had my period, I had sex on Jan.18 and everything was fine. My fertile window was from Jan.17-Jan.23 (we did the withdrawal method). On Jan.22 a bright red blog of blood came out. It was like egg white with bright red blood inside of it. That was the only time/day it happened. I have been feeling a bit of cramping,lower back ache and i have been peeing frequently. Period is supposed to come on Feb.4. Anyone know what this could be?