Hello, thank you for your question!
You mention that he hasn't had a bowel movement in about 1 week. Has he not gone at all, zero, or just small pieces? You have to make the distinction, because constipation (zero bowel movements) that lasts 7 days is a medical emergency.
If your child has still had some bowel movements, albeit hard and few, I would encourage you to visit a pharmacy. Your pharmacist may be able to suggest a product that is both effective and safe for your child. For example, there is PEG-3350, marketed under the name of Lax-A-Day, Restoralax, and others, which is a tasteless and odourless powder that can be diluted in a very small amount of liquid and given to drink once a day. The amount of powder is determined by your child's weight, 1 gram of powder per kg of your child's weight.
Your pharmacist.will be able to help you calculate the right amount to give, and document your son's chart for better follow-up.
Hopefully I have helped you, I remain available if you have any further questions!
Tom Samaha, pharmacist