It could be an intolerance, they do have quite a variety of symptoms, but it wouldn’t be my first thought. He could be not producing enough digestive enzymes.
The fact that you mention better stools first thing in the morning tells me that while his system is slowed down for the night, he has the time he needs to work on his food. This is often how it goes with dogs with nervous dispositions. You might want to look intotrying the Honest Kitchen’s Perfect Form. It has several ingredients that soothe the intestinal tract and one that may slow it a little.
When you have the stool checked on Monday, have them send it off to a lab for analysis. They find things that the vet doesn’t find on a normal stool check. And finally, you said he had worms this past fall. Did you see them or did the vet find them?
