The first week on Byetta can be marked by some side effects(ill stomach, nausea etc) and then this usually subsides. I am very glad you are feeling better overall and your sugars are improved, however I should mention that there is a small risk of developing pancreatitis(an inflamed pancreas) while taking Byetta. This can have some symptoms similar to what you described, although it usually does not come and go and classically is mid-abdominal pain. If you continue having these symptoms definitely call your doctor and arrange for a blood test to ensure you are not having early pancreatitis, because this can make you very ill, very quickly. Other possible causes of that pain which should be evaluated are gallblader, liver or kidney problems, and they may not be related to the Byetta.