He’s Christian and does all this stuff?

I’ve been with my now ex for 5 years he was not a good guy to me he cheated, lied and did everything he can to hurt me. Last year he started going to church because he wanted his family back I refused to go with him so I never participated church during that time. He was a “changed” man for a couple months till he fell for the outside world again he’d go to the club every week, drink and party. But still continued to go to church, this is why I never took him serious because from what I know your not suppose to do that. We got back together and his sister reached out to him and said we should probably get married because sex without marriage is not okay. So he broke up with me and now here I am heartbroken again. He recently met a new girl and she’s more of the clubbing type so he continued to do that stuff again and I asked him why? Why did you break up with me if your still doing stuff your not suppose too? His response was that he fell out of love and were not supposed to have sex outside of marriage. I’m devastated I knew I shouldn’t have taken him back