Another day, another problem

The other day my SO ordered a new phone. When he got everything set up i.e (social media) he said that everyone in his contacts were found. He came home from work and told me he had to delete his ex fiancé, baby mother, and a few others off of Instagram. Well, I was on Instagram today and suggest people to follow popped up. I click his baby mother page out of curiosity and saw a picture of her tagging him of their child. Now, I don’t have a problem with him liking pictures of his child, but he lied about deleting her and also liked a few other pictures of things she posted including a meme “when you’re done sucking his soul out, and he just sit and look at you after...” I’ve been though the entire “talking to other females stage” as I caught him having inappropriate conversations with another of his children(s) mom. We have kids together and I’m currently pregnant again. Any advice as I don’t want to go through what I’ve been through before?