Dry heaving can have a number of causes. Some are simple such as a furball
in the stomach and others are complicated such as fluid on the lungs
(cardiac cough). Can you get to a vet today and have his chest listened to?
That's vital. If it is fluid, the quicker you act and get it drained with
diuretics the better.
If there is absolutely no choice but to wait until tomorrow.. is he
breathing faster, and in discomfort? If so, then this is an emergency. Have you
any lasix in for him to take in an emergency?
[Non-text portions of this message have been removed]