Hi, My Bowel Motions Have Been Stopped For 3 Days

Hi,
My bowel motions have been stopped for 3 days and i'm feeling bloated and uncomfortable. I've been off my thyroxine pills for 3 weeks in preparation for radioactive therapy in a weeks time and am now on a low iodine diet. My bowels have stopped working several times in that period and restarted each time after a day or two.I've drunk a lot of water and tried lactulose and kiwi fruit to no avail and wondered about trying Epsom Salts