Advice needed

What’s the best way to end a relationship with someone? I don’t want to hurt his feelings so I can’t say the real reason, but to break it easy without sounding like oh “it’s not you” type of thing. We share a child together so I can’t just text him then block. I want to be mature about it, and coparent in a healthy way. He probably won’t be accepting of it because when I change my address I will have to notify child support because I do get state assistance and have to comply. I also don’t want to leave my baby in his care, I’m the primary caregiver and with him all day everyday. Any advice?