Af came early for me this month too. I started spotting 4 days before i was due and af showed properly the day before. I was sure something was up but my body was just screwing with me this month. Which completely sucks. Anyhow i too would suggest you start tracking your cm to see when you ovulate. And if you get really obsessed like me (lol) your could track your temps. Then you can really pin point it.

Good luck!!!