Implantation or AF?

Wednesay (4/2) I had the smallest amount of blood in my panties. I ignored it and never seen it again. I was due for AF yesterday (4/3) no blood, no sign, nothing. And today (4/4) I had red/pink spotting twice when I wiped. But it was about the size of a dime both times. Is this AF trying to make an appearace or is this Implantation? I tested yesterday morning and got a negative. I ovulated on the 20th.