My ex keeps messaging me saying he still loves me and everything like that, saying I’m his favourite person. I’m to scared to say I don’t like him straight up,

And I have feelings for someone else, how am I supposed to tell him without breaking his heart. When I was with him, we would have a on and off relationship. I was still friends with my ex and still talked to him but not often, and I understand that’s not exactly good. I would always go back to my other ex when we broke up, and I guess I never got over him. I still have feelings for my other ex and I know all my friends want me to be with my other ex instead of him. How do I tell him I lost feelings for him, and that I never got over my other ex?