Mildly alcohol dependent, starting rehab next week, if i dont drink at night i cant sleep at all. what medication is effective for this?

The safest would be : Melatonin. Because you are entering rehab, you really need to call your doctor for approval & dose. Congratulations on entering a recovery program for your alcoholism. It's a good place to learn healthy coping strategies if you're now willing to address issues & feelings you've been trying to avoid. Your gastroesophageal reflux symptoms will likely diminish a great deal when you stop drinking.