Thanks. We're hoping that's it. He's still sore today, but not as much. Tumeric seems to help, so I'm thinking maybe just a pulled/torn muscle. He sprained his leg not long ago and we don't know how he did that either... maybe the squirrels... so we applied heat, tumeric, and within about 5 days he was back to new. There are a lot of muscles in the back, so again, we're hoping for the best and that he just overdid it. He's such a power house and he jumped high for the tub (haven't seen that before) and was in pain that night, so maybe he landed on it wrong.
The economy has hit us really hard as a family and we're just focused on making sure our big guy has enough to eat. Hoping we don't have to take him into the vet, which is $68 just to be seen (3 weeks of feed), and then naturally they want to do all kinds of other stuff, which I'm sure is advisable. In the "old days" we could accommodate with ease. Now? Not so much.
Thanks for the replies. We'll give it as long as his leg sprain and see what happens. We don't want the worse to have to happen, as major repairs won't be doable. We really love this animal.
Anyone who feels like it can pray for our good dog.