Why is my period so light?

Gardenia

Hi all I started my period on Friday and I’ve been waiting for the flow to pick up but it’s basically been spotting for the past two days ( today is day 3 and it’s practically nothing). I’m so confused as this has never happened before! I did have sex in what I believe to be my fertile window but took 3 tests prior to my period starting and all were negative. I also believe I had a CP back in December so this is my second cycle since that, maybe that’s affecting my flow? Could i have implanted this late? (Bleeding basically started on my expected period day or a day early). Any other reason for a light flow? I’ve been drinking a lot with Valentine’s Day etc especially since I got so many negative tests, I would not want to then find out I’m pregnant and I’ve harmed the baby by drinking. Thanks