I started using Optimum 100% Whey Protein mix a week ago and within 2 days had hemorrhoids?

What is in this mix that is causing my hemorrhoids? I know it's the excess protein, most likely. Let me know. I bought a big tub of it, and I had been using casein protein (Muscle Milk) for a few months, and wanted to try whey as they say it's much more easily digested, but now my butt is paying the price. It's really painful. Should I stop it for awhile? I'm afraid to cut down on it as I'm afraid they'll come back after even a little of it. I've tried fiber capsules the last 2 days and hardly any crap comes out!