Endurance Riders: Please Read & Advise!

I would love if some of my endurance riding friends would share their thoughts on the following. At the Whiskeytown Race Blaze ate and drank like a champ and got As at preride vetting and lunch time. At lunch time the vet asked if he was eating (he was scarfing hay as we waited in line for said vet check) and said his gut sounds were a little quiet. Blaze went back to the trailer for our hold and had some mash and carrots. He peed and it was a fine yellow color. BUT after peeing he stretched out twice more and let his peeper down as if he needed to pee again. Nothing else came out. He seemed in fine spirits and ate more hay and drank as we waited for our riding partner to head out on the last loop. At the end of the ride he got all A's except gut sounds, the vet said there were almost none and asked me to come back in an hour. Took him back to the trailer and he ate loads of hay and drank, we went back to the vet and all was well, he received his A on gut sounds. He didn't do it again after that and ate and drank like a hog all night.
When I rode this Tuesday he peed twice in good color (one pre, one post ride) but after peeing at the trailer at the end of the ride, he again stretched out and dropped trou like he needed to pee again. He wasn't interested in hay or water (he NEVER is on training rides, hence my amazement at his eating and drinking so well at the race) but we got home and he ate rice bran and beet pulp and took off like a bat outta hell into his pasture and was trotting around grandly with his mini and seemingly feeling fine.
So, lots of details, but my main question regards the stretching out to pee multiple times. It doesn't seem like a good thing and I would assume signals discomfort of some kind (mild colic or??), but he seems to get over it quickly, he eats and drinks fine and is in good spirits otherwise....Thoughts????