I'm looking for a book, but I can't remember the title.?

It's a children's book about a boy that is scared of a monster that lives somewhere in his room, somehow he meets this monster and realises he's really nice and lonely and they become best friends. The last page has a picture of them snuggled up under a colourful patchwork blanket. It's really important to me that I find this book, so if anyone could help I'd be very appreciative :)