Do you trust your pediatrician? She said it's a stool softener so please stop calling it a laxative. The two are different. A stool softener helps the intestines to draw in water so that the stool gets softer. A laxative causes the intestines to contract and push out the stool. Big difference.
I don't understand what you mean about being "really irritating." The stool softener is really irritating or you feel irritated. I've not heard of a stool softener being irritating. From the way you worded the statement I think you mean that you're irritated with the pediatrician because she's calling a laxative a stool softener. There really are the two different ways of helping to have bowel movements and they are very different from each other.
My grandson has had constipation issues since he was very young. The pediatrician prescribed a stool softener that is now OTC and called Miralax. It helps many babies and children. You could try that. I know it's not irritating. Actually, it did not help my grandson but I've heard from others that it helped their children. And he loves milk and cheese and he has a couple of caretakers who didn't stop with the dairy products.
You do need to give the stool softener as prescribed. I suspect Miralax did not help my grandson because his parents and grandparents in 4 separate households were not able to be consistent in it's use. I dounderstand that if you don't expect it to work and suspect it's damaging that you won't use it as often as it's needed to be used. I urge you to rethink the process, as you're doing here with this post, and give it as often as prescribed and wait for it to work.
Continue helping him to eat foods that will provide the fiber and liquids that he needs to have a soft stool. He will need to learn to eat those foods if he is going to be able to have regular bowel movements. Also avoid constipating foods such as diary products (milk and cheese) and bananas. That means, ifyou're breast feeding that you may also have to avoid those foods. There are other foods to feed and with hold but I don't remember them any more.
My grandson still is constipated from time to time and nearly always has firm stools. He does continue to drink milk and eat cheese which seems OK since he also has regular, tho firm bowel movements.Others in my family have struggled with constipation there whole lives. You will be helping your son tremendously if you can help to get his body on the right track with regular, soft stools while he's young.
Remember: stool softeners work in a natural way with the body. Laxatives are chemical and can prevent the body, over time, to function normally. I have used stool softeners after surgery and found them to be very helpful with no side effects. I stopped using them, without difficulty, as soon as my bowel movements were once again regular.
I also agree with about the use of Benefiber and suppositories.