Could I be pregnant....again?

I had sex at 4 weeks pp. I’m now 7 Weeks pp and just wondering if I could possibly be pregnant again? I’m breastfeeding, and am not on birth control (only bc I’m getting the mirena iud and they won’t put it in until I’ve had my first period or am 8 weeks pp) I have not had my period yet so I’m not sure if I could even get pregnant yet anyway just curios since I’ve been nauseous and VERY crampy like I’m gonna start my period but then it never shows. Thanks in advance!