Is it normal?

I am 4 months postpartum & exclusively breastfeeding - I have noticed that sometimes after sex I spot.. for maybe 8-12 hrs (only there when I wipe). It doesn’t happen every time we have sex, but it only happens after sex. I haven’t gotten a period yet, but I’ve noticed this probably 4 or 5 times now. Is this normal or is this something I should talk to my dr about?