Oh goodness - I go through this with not only myself but with my son too. I have a beautiful 14 inch scar from sternum to pubic bone from a wonderful bowel obstruction 8 years ago
and we wont go there again - ever!
Miralax works better than any other type of Fiber thing out there. Problem with the fiber stuff is soluable vs. insoluable. One you have to drink a ton of water in order to get it to pass and stay bulky or you get constipated even more and the other, you wont have to worry about it at all. Miralax works without having to drink a ton of water and worry about it. You do need to drink water regularly, just not tons of it.
I give my son coffee as well when he gets constipated (which is quite often - lucky him, he has IBS-C too) but I add just a bit of chocolate Hershey's syrup to flavor it so he will drink it. It usually works within an hour and he never makes it through the entire cup. Fruit is another biggie - peaches, apples, pears, watermelon, etc. Bananas not so much as they actuall constipate more for some reason. Prunes, nope, he cant handle those either (neither can I) but plums we can both do oddly enough.
Laxatives are out as they cramp too much - although Milk Of Magnesia is okay but ewwww yuk - try getting a kid to take that! I dont even like it, so its back to Miralax daily, tasteless, ordorless and you can mix it in with juices and/or even koolaid and they'll never know
I also have to give him a dose of Gas-X or Mylecon Infant Drops (generic is fine) probably once a week (sometimes twice) as his stomach starts to hurt and it helps. He also shares my hot water bottle
- so now I have to get him one of his own, it does help.
Hope your little guy feels better sweetie, it is absolutely no fun, I know.