Should I leave my fiancé for my ex ?

I’m engaged and just had a baby a month ago and all of a sudden I feel like I don’t want my fiancé anymore. I was feeling like this during my pregnancy but my mom told me it was probably just hormones,but now I’m not so sure. It’s like the spark is gone and now I’m realizing maybe I said yes for the wrong reason and now that I’ve realized how big of a part his family mom/sister play in his business I’m kinda turned off. My ex has reached out to me and I know some might think he’s influencing these thoughts but he’s not because way before he contacted me I was feeling like this. He doesn’t know I had a baby yet but I do plan to tell him. I’m somewhat confused and very sad because there was a time I thought my fiancé and I would be married and happy but now I don’t know