DS will be 4 in a few weeks, and he is only sort-of potty trained. We don't have very many pee accidents any more, but poop is another story. He holds it and only goes every 4-5 days, and when he goes, it's immense. We give him a good dose of Miralax every day and often a dose of Ex-Lax as well when it's been four or five days. He can read, but pooping in the potty is beyond us.
His constipation may be purely psychological, but I recommend you seek medical advice, because:
1) Chronic constipation can be a sign of other medical issues
2) Habitual use of laxatives can lead to a lifetime of dependence on them
I have second-hand personal experience with both. My DD gets blocked up due to lactose intolerance, so as long as she doesn't drink regular milk ("But it's so good, Daddy, I couldn't help myself!"), everything flows fine. We know instantly when she's been consuming regular milk, because her belly is distended and feels very solid, and her appetite drops off significantly. Once she passes that milk blockage, she's fine again.
My DW experienced chronic constipation since puberty due to endometriosis. That problem is now solved, but the years of laxative use have left her with no alternative but to continue using them, because her body's physiology has adjusted itself to this outside stimulus. There should be warnings on the products indicating this eventuality.
