Mild cramping 4dpo

So my hubby and I have been TTC for 2 months. "Supposedly" I O'd on Saturday. We have been BD every other day. I thought I O'd on Sunday. However I woke up this morning with very mild but obvious cramping on the left side of my groin area. It caused upper thigh cramping too. Honestly I only get this a few days before AF. Has anyone experienced this before. The cramping comes and goes with basic discomfort of the lower abdomen.