19 months old always constipated
It's a good idea to review his diet, and put more vegetables and fruit into it. Drinking too much whole milk also can cause constipation. My son likes milk very much, he can drink 4-5 glasses of milk a day and he has hard time going to the bathroom. Old style oatmeal works good. Raisins, blueberry, apples with skin on, broccoli, squash and carrots are good choices.
limit milk and things hard to digest, including too much iron. Try a smoothie with a little kale and a bunch of fruits like apple, oranges etc. The kale has iron but leafy greens are great roughage. My experience with Miralax is that it doesn't work! Fiber gummies have helped my 7 year old but the key is DIET! Happy pooping ( :