The only thing I can say is that if you're already giving him enough space (and it sounds like you are) then there is something else about the relationship that isn't satisfying him.

Apparantly he says he's losing interest, well in that case I'm sorry to say this, but there isn't much you can do about it. I myself just broke up with my girlfriend for losing physical attraction to her, and I believe that if s/he is the one for you then losing interest won't happen.

Ask him for the real reason he's been losing interest, because space isn't the real reason.

If it's not something you can resolve, then move on- your true love is out there waiting for you.