Please help

I’m 4 months postpartum and I finally feel ready to resume intimacy. my partner and I started to he sex again, I noticed my breast milk flow has lessened. I used to get very engorged and had to pump twice a day and nurse with no problem, now I barely get 3 oz and I had to start giving my son formula because I feel like he is not getting enough when he nurses. My question is can sex affect breast milk production? Also I haven’t see my period since giving birth and im not on any type of birth control. Can I get pregnant if I don’t have a period?