Perhaps you could make an appt to see your dr and have a blood test done for HCG to see if you are pregnant.  If your not, then you can rule that out and investigate other causes.
I think its more than possible it can be implantation.  I had cramps from 10DPO last cycle and got a BFP at 14DPO.  That ended in early mc, but I have read that spotting and cramping are all signs.
Something else to think about is possible cyst from ovulation.  I have also had that.  Its when the egg releases quite violently from the ovary and fluid builds up in the follicle and turns in to a cyst.  Symptoms include, late AF, cramping, dizziness, spotting and nausea.  All symptoms of pregnancy. 
Good luck 
