implantation or AF??

Carys
Had really bad cramps the last two days and now this this morning. Unusual for me - usually AF comes in full force! I'm 11 DPO and AF due either 9th or 10th. I'm going to take a PT tomorrow morning. Could this be implantation bleed or is 11 DPO too late for that? Please help, I'm driving myself mad :(