Implantation or AF?

I’m 12/13 DPO today. Had some light cramping last night and mild cramps this morning. Cervix is high, medium and tightly closed. I just went to the bathroom and there is light spotting. Usually my cervix is medium height, medium firmness and slightly open. my periods the last few months have been on the heavier side when they start out and it’s bright red blood. The spotting I had today was dark red/slight brown ting to it. I know I might be AF, but wondered if this has ever happened to someone and they still were pregnant. I haven’t tested yet and I’m too afraid to, just to see another negative.