When I wasn't successful in nursing (and it was extremely hard for me to give up) we turned to formula. For weeks our daughter (at the time 2 month old) would go from calm to screaming as she would pass gas. As I was around more and more other moms they told me that it wasn't normal for her scream that hard after eating and passing that much gas. My cousin said that all four of her children were on soy formula because of gas issues and it solved all their problems.
I called my pediatrician and he said we could switch to soy, no problem. If our daughter had an constipation issues from the soy formula to just give her apple juice for one of her bottles a day.
We did and it was a miracle worker! She didn't have tummy issues anymore, was so much happier and the apple juice helped with constipation!
*I am not a pediatrician so always check with your doctor before changing anything with your child's diet.