Implantation bleeding or late pp bleeding?

Okay so I am currently 6 weeks postpartum and my husband and I had a moment and ended up having sex 3 and a half weeks postpartum (bad idea I know) but anyway I thought I may have ovulated about 4 days after that and now I’m experiencing lower back pain cramps in my lower abdomen and very light pink spotting but only when I wipe. Could this somehow be a late implant and I could be pregnant again? Or could this be late pp bleeding or maybe even ovulation?? Anyone else ever experienced this after birth?