Period,going for a number two and oversized stomach

Patient: I have weird period dates, they go like:12th-17th one month then 15th-21st the next month then starts at 12th then the next month was 17th, also im on for 3 days, off the 4th and back on the 5th for a day.next i go for a poo like 3 times a month, only when im either coming on, on or coming off my period.also, only recently has this started happening, i have been able to eat sooooo much and i dont get full up, i am also getting alot fatter.

Doctor: