When a man says he just needed some space or down ...

It might be that he feels the need to be alone and complete his chores, and it might mean that he needs to be alone just for the sake of enjoying the quiet.

It could also mean that he's looking for some time away from his current relationship, in which case it might be worth while to look into the relationship, and see if it is indeed too clingy and suffocating.  

This might be a hard bit to swallow, but here's the truth straight from the horse's (or man's, in this case) mouth:  No matter how much we might love you, and no matter how much we might want to spend every waking moment with you...if we were with you 24/7 we'd go freaking insane.  Men and women are different, everyone knows this, and it's amazing that we've survived as a species at all, let alone become the dominant force on the planet considering how poorly men and women get along most of the time.  Because of those inherent differences sometimes we need, and in fact crave, time to ourselves.  I'm sure, though you may not realize it, there are times when you'd just rather not have him around, and want to think about girly things when he's talking about monster trucks and nascar (or whatever he's into.)  Same goes for him...there are just certain things I can't seem to concentrate on when my girl is there, like the plans i'm working on for an electromagnetic rifle, or a flying car that runs on motorcycle engines, or just how I'd turn an 83 diesel mercedes coupe into a swamp buggy...she's so far off the frequency of those thoughts that I start thinking babies and curtains and it screws me up :)

I believe that he may want to have a break from your relationship so he can do what he needs to do whatever it is, or he is possibly  not sure about your relationship. how is your relationship? Are you aware of  any reason for him not to go through with it?

it means the relationship is about over.