4 weeks pregnant

Cora • Mom of three💖💖💙 | Licensed Hairdresser🖤

I’m 9 Weeks PP but just found out I’m 4 Weeks Pregnant. I didn’t have sex until 6 Weeks postpartum so how am I 4 Weeks? I even had my period at 5 Weeks postpartum well into 6 weeks so there was no sex at all. Am I just miscalculating when my period started?