radiation damage

hello in 2015 i had a radical hysterectomy 33 radiation treatments 3 internal due to uterine cancer that spread to the cervix and upper vagina.for the last two years i have not been able to empty my bowell i was told in 2016 i had proctosis .in order for them to check me they want me to drink a gallon of liquid  which they dont seem to understand my come out and may just sit in my stomach its as if there is something blocking the way i spend a ungodly time in the bathroom for basically nothing.its only lil bits that pass no consistany.im begining to think that this will be the death of me im so bloated its unreal which im pretty sure its because im literally full of s**t.(sorry) no other way to explain this.am i the only person this has happened to?these drs dont seem to understand what im saying i cant live like this much longer before something gives way idk like my bowell.any advice would help im suppose to see a new dr in augest which im sure he will think i can drink gallons of laxitive but there is no way.thanks in advance and sorry if this was over the top but im getting desperate.