I’m proudly amateur in my approach to all thing Audio! I have a bedroom studio too, which is a little bigger at 5m x 4.5m. I’ll add that I’m not an expert in this area, but I have spent a huge amount of effort getting my room to a point where I can at least trust my ears when I hear sound coming out of my monitors.
I’ll agree with about the monitors being too close to the walls. In my bedroom I could only move them about a foot away from the wall while still maintaining a usable room. So I pulled my desk away from the wall, and pushed the speakers further towards me so there’s a distance between them and the wall. That really did make a huge difference, and I don’t think I could go back to putting them up against a solid surface again. As I mainly do vocal recordings, I had to make sure that the big fat solid walls directly in front of my face had some foam squares on them. That also really helped a heap with some weird echoes I was experiencing. In terms of bass traps, I built some rockwool absorbers, and ended up with 8 of them in the room. Each one is a fairly decent size, and depth. In front of me I have 5 of these traps, 3 in the corners, and two on the upper edge hanging from the ceiling at 45 degrees. Above my head I have large “egg carton” foam panel, as first reflection point treatment, and on each side I’ve got panels at my first reflections.
On my left side I have a window I can’t move, so I decent heavy curtain which seems to do a good job of cutting out reflections. The rest of my bass trap absorbers are in various places around the room. The back wall in the room is a horrendous built in wardrobe that just presents the room with an amazing smooth and reflective surface for all sounds to bounce off and ruin my listening! I tend to leave the doors open and let the odd objects in the wardrobe act like natural diffusers.
I also have a rather large sofa bed, and I just count it as a opportunistic broadband absorber that you can sleep on.
I spent months working on this room, and I won’t pretend it’s anything other than some amateur fool’s attempt at getting a good listening room. But I will say that going to other people’s studios and listening to stuff is nowhere near as satisfying as sitting on my chair and firing up some music. Over the years I have got extremely confident in what I’m hearing from my monitors and making choices with my EQ. I think that’s the important point here. Get your treatment done, and then get confident with what you’re hearing coming out of the monitors.