how to tell a guy I just want to be friends?

I’ve been in a really bad place after ending a 5 year toxic relationship and I genuinely feel like I can’t be with anyone because I just need to be by myself I guess. So an old friend I kind of had a “thing” with before I started dating my ex hit me up about a week ago and has been snap chatting me pretty much every day and I’ve kept it as casual as possible and we said we would hang out soon and catch up but he just sent a Snapchat calling me cute and now I feel like Ive definitely led him to believe I want something more. I feel awful and I care about him a lot and don’t want to hurt him. how do I do this