This just happened to us recently. Our dog ate cat poop and some of the litter got stuck. They did some tests, put her on antibiotics and fluids. Yes, it was about $600, but worth it! If you have to, just have them do an xray to see if there is pancritis or a blockage, then decide what to do from there. That was only about $100.
Dennis, this type of problem can turn so serious so quickly, I suggest calling your vet right away. There are many different things that might be causing it, but guessing wrong could endanger your dog's life. If you don't have the money, beg or borrow enough to get him to the vet ASAP. Good luck, and keep us posted on his recovery.
Login using the form on the top of the page to post feedback (if you are a registered user). If you have not yet registered, click here to do so. It's FREE!.