Suggest Treatment For Painful Urination In Children

Hello, My eight year old son sometimes has painful urination, blood stains in his underwear and at lease once a week chalk white stains in his underwear. The painful urination and blood stain are less frequent no the blood stains small and only a few. He further has almost daily incontinence problems with small leakage into his underwear causing him to need to change frequently. Our doctor hasn t found a reason no I would appreciate ny advice. Thank you!