my ds2 is only 3.5 but the constant wetting the bed drives you nuts! i put pull-ups on him, and 9/10 he wakes during the night takes it off and ends up wet regardless.
could you limit his fluid intake befor bed? it hasnt worked on my ds2, but could help work for you? also waking ds1 befor we went to bed, just for a quick loo stop worked for him, not for ds2 but! good luck, i hope he figures it out soon for your sake!