Jeanie, read this link:
How to Treat Prednisone Side Effects in Dogs on Steroid Therapy | Suite101.com
Steroids do upset their tummies. Perhaps the dose can be adjusted to make him more comfortable.
My vet used to tell me to give pepcid for an acidy tummy. It was just something that we would give very seldom though. It wasn't a frequent thing. What I think it does is break that constant chain of acidity and then they are ok usually. However, since Tibbe is taking the steroid, I think that is what is causing his tummy problem.