Please be sure to inform all the physicians involved in your current care plan in this evaluation, if in fact you are being cared for by more than one physician.
Although you don't indicate what caused your abdominal pain or how it is being treated, I suggest that you reevaluate the use of Ambien CR as a sleep aid with your physician.
This problem requires two factors: a pill or capsule getting lodged in the esophagus, leading to a prolonged period of contact, and a compound that is either too acidic or basic for the esophagus.