HELP! Implantation Bleeding or AF start??

This is my first time posting and I see this question *in different ways* all thru this community... so, don't be mad at the repetiveness!

I am almost 23 & have been TTC for 3 months. I have been in my ovulation window up until tomorrow and have been having sex every other day in my window. My period isn't due for another 8 days but I have been experiencing light brown spotting since yesterday after sex *PEAK day*. It's not a flow just when I wipe.

Could it be implementation bleeding or AF starting early??