Hello I am trying to remember a book I read as a young teen/tween age (may be a series I'm not sure) and I almost gave up, until I saw someone post on a different subreddit with what I'M 90% SURE IS WHAT IM TALKING ABOUT, but it wasn't solved and they are banned from reddit now. The book is about a young boy (I think) who is being chased or is involved with monsters somehow, and is being hunted by this humanoid monster with a stitched mouth and I think a hat? and again I'M 50-80% SURE it turns out somehow that monster is an imaginary friend he drew when he was younger and it wasn't trying to kill him, or it was and then it wasn't I'm not sure, I think he was on the cover of the book. It's driving me up a wall PLEASE if anyone thinks they know it please let me know.
Edit: SOLVED by myself, it's called Invisible Fiends (series) Mr Mumbles by Barry Hutchison