My MIL had never tried Splenda, so I made some almond cookies for her and she was ILL. She couldn't leave the bathroom for hours. I felt awful!!
I would try leaving it out for a while to see if it helps. Try Stevia root extract, a natural sweetener. It comes in powders and liquids, some of the powders even contain psyllium as well. Some people take it as a suppliment, but I'm not sure what for. I have never heard of any ill effects from it. In Europe is is commonly used in baking now, but US industry relies too much on sugar, so it will probably never become as popular here.