Spotting after my period?

I got my period on 8/9. It was really short. Lasted only 3 days pretty much the forth day wasn’t much of anything. I had sex with my bf on 8/14. Literally 1 days after my period. On late evening of 8/21 through 8/24 I had mild cramping and spotting. It began like nothing, I wiped and it was pink. Then the second day it was brown, so I though oh maybe it’s my period again. But then it went back to pink. I’m really confused because my moms side of the family says that sometimes you can get pregnant right after your period. But I’m not so sure about that. Can someone please give me some tips or has anyone else experience this?