Found out fiance is cheating 2 days after our son turned 1

I cannot believe this is my life. I do everything for him. Cook, clean, fix his plates for work and when he gets home. I work from home and do 99% of the childcare. He maybe changes one diaper a week. He’s given him a bath a total of 3 times in his entire life. We’ve been arguing a lot recently, he’d get off work and spend 3+ hours at the gym not coming home until me and the baby are in bed. He’d spend whole days off away from the house. I should’ve saw the signs sooner. I feel like an idiot. Now I’m uprooting my entire life and moving into a tiny rent house when the house we were living in was supposed to be our forever home. We just moved here 2 months ago. I poured my heart and soul into the renovations of this damn house and I did it all by myself. He never lifted a finger to help. And now I have to leave the house I built for us because he wanted to tear our family apart. Cheating is a hard line for me and it’s one thing I’ll never forgive. Not to mention, he had absolutely nothing to say when I found out so it’s not like he wanted to fight for our family anyways. I’m so hurt, disgusted, disappointed. The only thing holding me together is my son. I know he deserves better than a father who would rather spend his time trying to find a new family than taking care of the one waiting for him at home.