He is a compulsive liar!!😡😢😢

So I'm 32 weeks pregnant and through out my pregnancy my SO have been great! I mean more than great he is just in love with this pregnancy as much as I am. However, we have history. I've been with him for 5 years and I have caught him cheating several times and my stupid ass forgave him and we decided to work it out and move on until flashforward to today. Last time he cheated on me was 2 years ago ( as from what I know) but lately I've been getting that 'feeling'. You know that feeling that us girls get when something is up. Well we promised each other awhile back that we should not get on our Facebook anymore. Well today I just needed a peace at mind and finally got on mine to see if he has gotten on his and sure enough....he has! He just added a picture of himself and a picture of our new car. I'm pissed😡 I mean why can't he put pictures or post of him being a dad if he is so excited? I'm a with a two faced person? I swear I just want to go crazy on his ass but I can't because I don't want to cause any stress on my baby. I can't believe he is going back to his usual ways, I mean I thought he really changed he is working really hard for us and the baby and is super excited but now idk. I feel so sad, I feel like this baby will be born with parents with problems. One who keeps lieing and the other that can't trust the other. I haven't confronted him yet but he knows something is bothering me. I need advice before I make a stupid decision!