Oh hun, it sounds horrible, it's bad enough for me when DD occaisionally has a bit of constipation, let alone so badly. Your poor little man.

Have you tried all of the natural ways- warm water to drink, plenty of water, prunes/prune juice (diluted- not suitable for chn under 9mths), pear juice, bran, lots of fibre-fruit/veggies, exercises to help move things (cycling his legs, touching his opposite toes to hands...), tummy massage, avoid rice cerials, rice, bananas- they can cause constipation, make formula correctly to specifications, 1/2-1 tsp brown sugar in 50mls water (always works for my DD).

I'm sure you have tried them....but thought I'd ask