Digestive Cramping with Blueberries

My questions are: why is it when I eat fresh blueberries, with or without blueberry yogurt, I experience extreme cramping? The cramping will last anywhere up 6 hrs. Occasionally I have mild cramping the next day.
Are there other berries I can eat without cramping?

It is possible that you are eating too many bluberries. People who are not used to much roughage in their diet do experience cramping when adding too much roughage at one time. Try eating only a few, increasing the number every week. If this still causes cramping, then there is an incompatibility between you and blueberries. Anyone can have adverse effects with any food. The reason cannot always be determined.
Regarding other berries, try eating one or two raspberries or blackberries to see whether they cause cramping. I recommend that you discontinue any food that causes you digestive problems, but if, in your case, you do not normally eat much roughage, it is important to your health to add roughage (fruits and vegetables) to your diet very gradually.
A consultation with a medical or clinical herbalist or naturopath can help to determine whether you have any digestive problems by performing a complete assessment of your health.