My sisters kids just had an endoscope done to her, she is 4. She has been having issues for a while, but also get blood in her normal stool or is really runny. We are still waiting on results from her test, but yes that is one thing they are checking on.
My hubby is lactose intolerant... if he drinks milk or eats cheese or icecream he gets really gassy, not really "farting", but gas pains sometime so bad that he can't even walk. It also causing him to have to run to the bathroom a lot, once its out of his system the gas pains go away & all is good again. But no he hasn't had a doctor tell him he has an issue, but when he doesn't eat anything with milk - he doesn't have any issues... do we really need a doc to confirm.
We had to watch which formula our 1 yr old had cause of his gas pains... we ended up using Carnation Good Start Gental - it was the only formula out of 8 that we tried that didn't cause him to gas up and cry all the time. So, far we haven't had any issues with milk, but I drink a lot of milk so maybe we will luck out and they won't get the intolerance from daddy!
I'd keep a log of how much milk and milk products your boy drinks/eats and one on his tummy hurting. See if there is any differences on days you give him less milk and milk products and days he gets more. Watch it for a month or so & if you see a pattern make an appointment to see his doctor and take the logs with you. They maybe able to get you more information or testing to help him and get to the bottom of the situation for both him and his dad.
Plus, if the doctor does do a diet change for your son, maybe you can talk your hubby into trying it since he is such a role model for your son... thus in the end helping with one of the annoying factors dealing with your man - lol. In the end everyone wins in someway :)