When I rub my penis and even do not masturbate I get lower abdominal cramps?? if I masturbate I get lower abdomen cramps and constipation

Seek medical exam. you should not be suffering these symtoms from masturbation. Please get examined and treated.
Constipation. Seems your primary problem is constipation. Drink plenty fluids, eat plenty vegetables, decrease fast foods and snacks, get plenty activity, and that should keep constipation under control. Prunes and prune juice can help. See your clinician if still problems. Hope that helps.