Withdrawal bleed tmi

I’m on the pill and I take it perfectly. I had sex several times this month aNd I started my placebo pill today. We always used condoms and he pulled out. IM pretty sure the condoms never broke. I started my withdrawal bleed today and it was bad enough that it left a pretty heavy stain in my underwear, but now about 8 hours later it’s stoped for the most part. Was that my withdrawal bleed and I will probably get more soon or could I be pregnant and that be implantation bleeding. I was bleeding heavy enough that I needed a tampon for a couple hours and when I replaced it and took the new one out, it barely had any blood