Wow.. well if he does have ulcers is there anything we can do about it?
absolutely! Also, your vet may decide to treat even if ulcers are not seen in the stomach as they can also be in the intestines. Based on physical exam and history, they will help you decide what is right for your guy.
Treatment is typically omeprazole (Gastroguard in horses, prilosec in humans) and given for 2 weeks. After treatment, you can put him on an ulcer preventative. Two that I like are U-guard and smart gut, both from Smart Pak and both very affordable. The Gastroguard on the other hand is very pricey but ulcers are serious business and need to be addressed.
I also agree with others about having the chiro out, making sure the girth doesn't rub, saddle fit (I know yours fit him before, but if his back is changing the saddle fit will change with it).