What a strong little one you have there! Sounds like you raised a brave and articulate youngster, and don't ever lose sight of that! You are so lucky that he feels comfortable enough with you to tell you exactly what's bothering him, instead of holding it inside, letting it build up and come out as dysfunctional behavior sometime later.
Well, nothing like hearing the truth from the mouthes of babes, eh? Maybe this will become the one spark of motivation to really push that cleanup project out of the planning phase and into accomplishment!
Just keep thinking about how happy both he (and you!) will be when all the clutter is gone, all the dirt is cleaned up, and all the remaining useful things are put up in their place!