Yes I have been there too with TJ and I agree with Wylie's Mom, that this is quite painful. There is obviously a digestive issue. Get a full blood panel done. Also what food and treats are you feeding? He may need a minimal diet and no rich foods or treats.
TJ had an over growth of bacteria in his GI tract. After many different trials and errors, we gave this a try: Tylan Powder ~ ask your Vet about it
...while it worked for TJ, it didn't work for others....BUT I think it is worth a shot
Keep us posted