my dad had this sugery two years ago and alos went thorugh what you are describing. i dont know exactly how long it lasted but im thinking the first six months to a year were the worst. now it seems that it is not an issue for him anymore but he does have sensitivly to foods and gets the runs more often than he would like. he is more in tune with what is causing these episodes and trys to keep the food intake like milk to a minimum.
be patient it gets better and the first year is rough but after that you will return to feeling much better and understanding how your new body parts works. Hang in there!