Pregnant and dating, when should I mention it?

Okay.. So my baby father also dad to my born child has cheated over and over keeps going back to his side chick and I've decided it's time I move on before I have another lonely pregnancy, I need someone to make me happy forever not one night here and there.. Its hard for me to meet anyone as I don't got no friends new to the area and breastfeeding my son.. I met this guy online with twins and he seems great! I just don't know how or when to tell him I'm pregnant, today is the first day we've spoken properly trying to get to know each other he's supposed to be calling me later!! What should I do?