Implantation pains but a BFN

Hannah • TTC #1 since January 2014
Just wondering of anyone can help? This month I had what I thought were
​Implantation pains at 6dpo and then on and off since then. I gave in today (13 dpo, AF due in 2 days) and took an hpt as I just knew AF was on her way based on my cm checks and wanted to confirm a BFN to get it over with. (This was also my last month to have a baby before I'm 30 so a bit of an emotional one) It was a BFN as I expected but now I'm wondering why I've been having these twinges for the last week? Does this happen to anyone else?  If this is going to happen every month I'm going to have to learn to ignore it as it obviously not a sign of pregnancy for me :( Any advice ladies?? X