I feel a throbbing pain in the anus. Please help me.

Hello doctor,

I am a 29-year-old male unmarried. For more than one year, I feel pain in the anus like throbbing (pain like beating in the anus) and feeling huge pain four hours after masturbation. The pain continues for five minutes or 10 minutes and gradually reduce and stops. Pain rarely comes. Sometimes, without masturbation also but if I masturbate pain definitely comes. It starts at midnight or sometimes in the day. I always drink plenty of water. I never feel any pain or any problem in passing stools. I am having type-1 diabetic and taking insulin injection for the last 13 years. I am taking insulin three times and I have my diabetics in good control. I do not know what type of problem I have. Which type of treatment is required? I am afraid of what might happen if I enter into a marriage with this problem. Please help me.