Pregnant?

So apparently I’ve been taking antibiotics that can reduce the effectiveness of my birth control and I was not made aware of this. I had unprotected sex three days ago and today I’ve been experiencing some cramping. This is what I find on my underwear. I have bacterial vaginosis so that’s why I’m taking the antibiotics. I’m On day 5 of 7 on my antibiotics so is this from the bacterial vaginosis or implantation bleeding or what? please help. Thank you