Implantation or period?????

So last night (sept. 30) I was sleeping and I was rudely awakened by nasty painful cramps and I couldn't seem to get comfortable and eventually I fell asleep. I'm 12dpo and I never got any cramps at all this cycle, my period is supposed to start either tomorrow (Oct. 2) or the day after (oct. 3) so I'm wondering if it could have been late implantation or if it's af rearing her ugly head? I've heard implantation could take 12 days. Also I didn't get a bfp with my first until late into the fourth week and I'm only 3w2d in so far. What do you think???