My cycle is incredibly irregular and it just comes when it wants to. My apps try to predict it but it's never that accurate. I track ovulation via BBT and ovulation test strips. Today while I was working, I felt a very sudden dull throbbing ache on the right side of my abdomin (before that I have had "twinges" going on but nothing painful or anything to really write home about). It only lasted a few minutes and stopped. I went to the bathroom a few hours later and there was the FAINTEST patch of pink on my white undies (TMI) and it barely made the tissue pink when I wiped. It hasn't happened since and that was around 2 pm (currently 7pm).