Implantation bleeding

Hey, so basically i took plan b three weeks ago. Didn’t have any symptoms except for fatigue and mood swings. Now three weeks later i have gotten what seems to be my period. However it’s rlly different. I have no cramping, it’s red but watery. A little bit of clotting. I’m so confused and a little bit worried if it’s implantation bleeding. It came a day before i got my period last month, so it’s pretty on schedule. What do you guys think?