Implantation or withdrawl

So I just switched birth control pills a month ago. I was on one that only had two placebo pills and now I have a weeks worth. I didn’t have a period with my last kind of birth control but I started my placebo pills Saturday and today I have like a brownish discharge. Is this the start of my withdrawal bleeding or implantation. My boyfriend and I always use condoms and he pulls out. So the only way I could be pregnant is if the condom had leaked precum. It never leaked when he actually finished. What do y’all think? Should I worry?