Implantation bleeding or light period? Help!

Hi guys. So about two and a bit weeks ago my partner and I had unprotected sex but he pulled out. I took a Plan B any way just to be safe. I’ve been experiencing cramps and am supposed to get my Period tomorrow although my cramps started today and I have light pink/ brown discharge. Plan B usually skips a period for me but i was ovulating in the week that my partner and I had intercourse. I’m just a bit confused as either the plan b didn’t work and i should be getting my period normally or i should be skipping one. Is this possibly implantation bleeding? The chances are low so I’m doubting it but I haven’t ever experienced a “period” like this. Could it be the effects of the Plan B?

Thanks