I was having problems with stomach spasms, gas, and bloating. I saw a doctor who told me I have gas and not to use Benefiber because it can cause gas. I tried this and it really didn’t help. Finally I decided to cut out all artificial sweeteners and foods and drinks that contain them, (mostly low-fat, sugarless items). After a few days my stomach problems dissipated and now it has been two weeks and I have not have any problems.
I suggest that if you are having gas and bloating problems get off the artificial sweeteners for a while and see if it help. It is easy and cheap.
Good luck!

Most of what I read on digestive problems seem to always suggest limiting refined sugar intake and eliminate the substitutes. The artificial sweetners are also listed as an aggravater for IBS sufferers. I use Spenda for my twice a day decaf coffee and I don't drink sodas. I did eliminate all the sweetners for awhile but didn't notice a difference so I went back to the Splenda. I would guess that a lot of people would benefit from some kind of elimination diet to determine if they have allergies to certain foods, drinks, ...