AF or implantation bleeding

So I had some light bleeding today that might be AF starting or implantation bleeding. I'm 4 days late today. I'm not having cramps tho. I haven't had cramps all day. I usually get cramps an hr or so before or right as soon as I get my period, but no cramps! N it's not heavy. But it's red. I'm so confused. The cramps i usually get feels like bad pressure all over my lower abdomen. Any ideas? Please help me!