implantation or af?

On Friday night I had these really odd feel cramps, it didn't feel like af cramps and when I went to the bathroom there was pink when I wiped. Cramps were on and off throughout night and Into the morning, when I got up to use the bathroom it was darkish blood. And no more bleeding or pink after that. AF is due today, but no sign so i don't know.. do you think implantation or just early af?  We are ttc for our 1st so this is all new..