Son Bedwettin last 4 years, please help.

My son started wetting bed at age 7 and is still wetting every night. Many time twice. At around 1am then 5am. He has very deep sleep since birth, otherwise active and normal. Other medical conditions 1. 8th month premature birth weight 1.3kg 2. Appendix surgery age 4 3. Undescended testis both at birth , surgery at age 5 4. Only one testicle found/transplanted, and other dissolved. 5. Had severe allergy problem from age 4 to 8 during season change twice every year, cough-sneeze-vomit We have taken treatment in homeopathy and ayurveda for 1 year duration each. But the problem still persistent. Food only home cooked no spicy oily nothing given to child. Went to couple of allopathic doctors but one provided nasal drops at night and another doctor recommended minirin. We are not sure of this drug. Tests: Urine, blood test, ultrasound abdomen and urine pre and post void done, found normal Please help and guide.