Pregnant at 3 months postpartum ?

I’m 3 almost 4 months postpartum and have a small thought I could be pregnant again. This is my 3rd baby and my last 2 were breastfed but even then after 6 weeks postpartum I would get my period right away and back to normal month after month. This time around same thing I got my period right after the 6 weeks and that’s it haven’t gotten another period. Is this normal or is it possible I could be pregnant? We did have intercourse just once after I had my period so hoping I didn’t end up pregnant from that one time lol.