My child is a consistent bed wetter. What can I do?

My child is going to turn 6 and he still wets the bed. There are months when he doesn't pee on the bed at all and even wakes me up at night if wants to pee, and then there are days when he wets the bed not only once but during wee hours as well. What I do is always make him pee before he goes to bed. And also that he sleeps early than me, so when it's my time to go to bed I make him pee once more. http://www.webmd.com/children/features/bedwetting-causes