Constipation and fissure problem.

My son developed constipation when he is 1.5 yr old due to buffalo milk.since then his problem is not going away.i have used laxatives mu out powder 4 spoons and smuth syrup 15ml in night and giving proper diet and water but also he feels uncomfortable while pooping and complains about severe pain and afraid to poop.His stool is not very hard like stone but starting poop appears to be light hard and remaining is soft. He is suffering daily and very much afraid to poop due to severe pain.Iam also afraid of these medicine are habit forming and have any side effects in future due to regular use.I want to stop medicine and work on this naturally but afraid of hard poop.Does 3yr old kid require surgery for chronic fissure and can they bear this pain Iam worried