diarrhoea in a 2 and a half year-old

 
A bit of a background on my son. I had polyhydrominos (excess fluid level of 29) diagnosed at 30 weeks pregnant. My son now two and one month developed breathing problems at 2 months.  (sounded like a 60 yr old smoker with emphysema) This breathing difficulty including stopping breathing intermittently went on undiagnosed for 7 months despite doctors visits and hospital visits two to three times per week. Finally he was diagnosed with a trachea which is half the size it should be therefore restricting breathing when he gets cold etc. He also was diagnosed with pnemo virus?? Which is the reason he was actually admitted to hospital ( this virus only lasts two weeks though) During his hospital stay they discover he also had Hydrocephalus which has since been changed to "benign enlargement of the subarachnoid spaces" and he is seeing a neurosurgoen regarding this who is doing MRI's at 3 month intervals to watch the fluid levels.
 
My question is he has diarrhea nappies approx 6 times per day every day. I have told numerous doctors this and all but the last one a paediatrition ignored this and said it must be his 'normal'  The last one said he is maybe lactose or fructose intolerant and to put him on latcose free milk to see if that helps. We have done this now for 3 weeks and there has been no change if anything his poos are worse. They are a milky white slop and frequent overflow his nappy. He is off his food two out of three meals and even then we have to 'prime' him like a lawnmower and force the first bit into his mouth to get him to even start  to eat. As a baby he was a hungry little bub and ate 2 hourly. I am at a loss to understand what to do for him. I end up cooking and offering a few different meals at each sitting hoping he will eat one with gusto. He if he had his chance would drink milk all day. I have decided to limit his milk to half a bottle to try to force him into eating solid food. I am open to all ideas and suggestions.

                       You and your son have had quite a time of it and I feel sorry for you.
As regards the diarrhoea and poor appetite, I think he should have a microurine and colony count done to look for a urinary tract infection. If that is excluded then I would try withdrawing fructose. This is done by stopping all fruit, including fruit juice for 3 weeks.
You might ask what is he going to drink and I would allow him a little milk and plenty of water. Hopefully this will improve is appetite for other solids.
How is he growing by the way? Please let me know what happens. If he has no urine infection and does not respond to the fruit withdrawal, there are other things that can be tested.
When did the diarrhoea start and did it have any relationship to dietary changes such as introducing cow's milk formula or adding solids to his diet?
David