You probably either had him in the wrong
position for the
enema or you were using the wrong kind of nozzle (those douche types which spray on all sides are best avoided - get one with one aperture at the top).
Anyway - an enema is what he needs.
And after that - try every dietary tip you can think of (lots of fruit, green veg, pulses, nuts, brown bread, muesli) and - importantly - keep him as physically active as feasible (at no age is it ok to be a couch potato)!