Hi Emily, My husband told me not to get lawyers involved and than turned around and had me served with divorce papers 5 weeks after he left. You can CONTEST the divorce for 2 years in PA. I know because that is what I am doing. DO NOT worry about him filing for divorce. Worry about you and the girls. Go to court and at least establish CC and CS if he is not giving you money for bills and food and clothing for the girls.
My H is living with my "friend" (3 weeks) after he left and we caught them together (2 weeks after he left). Do not worry about them - it will end in its own time. Let it take its course - you do not have a choice. Give him enough rope to hang himself.
I have not spoken to or seen my H in 4 months. He will call about the girls if he cares. Just be nice and calm and do not bring up the OW or your R. Please calm down and be happy you are only hurting yourself. Everyone here does care about you and they worry.