15 dpo possibly pregnant?

I think I'm about 15 dpo. AF was due yesterday. This morning I noticed a tiny bit of pink when I went to the bathroom. I almost didn't notice it. I thought AF was starting and got a tampon. Later I went to the bathroom and only had a small bit of brown blood. Nothing when I wiped. I just went again and there was a bit of pink when I wiped. I can't tell if AF is playing a mean trick on me. I was just wondering if anyone had an experience where they had light spotting when their period was due and ended up getting a BFP