My son is 5 years old nausea, vomiting, loose motion, accompanied by constipation?

my son is 5 years old. He is suffering from severe abdominal pain for about 3 years along with nausea, vomiting, loose motion, accompanied by constipation. He resists urination to avoid pain. According to local doctors there is viral infection because of excessive retention. There is no cure yet so far, we can send you the reports