Do you get stomach problems when you first get on, maybe for the first week and a half or so, and then it goes away, or do you get problems the entire time you are on it?
I have experienced similar problems with Monohydrate, but it always goes away quickly. One thing that helped me was to take smaller doses, 2 times as frequently. So instead of 5-6g at once, take two 2-3g servings spaced out a little bit. This helps with feeling bloated, too, because you don't need to down as much water all at once.
Besides Monohydrate, i have heard that ethyl-ester works really well. Just watch the time that it spends in the water/drink that you mix it with because it turns into toxic creatinine.
good luck man