Possibly pregnant or should I just relax?

My fiancé and I had unprotected sex and he came inside and we weren’t able to get emergency contraceptive until a little after the 72 hour mark. (Ik so stupid but we were on vacation and weren’t able to get one. We don’t want kids really right now but if it did happen we’d be okay with it.) anyways that happened and I took it as soon as I was able too. That was a little over a week ago and I started spotting and it’s pretty brown and super light. I also already had my period a week and a half ago. I’ve only had plan b one other time and had no side effects at all so I was just curious if anyone has experienced this before, has anyone gotten pregnant when they took plan b? Tell me your stories please!