Long story short I've been having some issues with my now 4 year old for the last four months. Namely stopping and refusing to move under saddle and some uncharacteristic spookiness. I've been working with my trainer, had multiple chiro, massage, PEMF treatments, lameness exam all that and we have made zero progress.
It could be lazy baby shenanigans (he's been under saddle for 8 months--the first 4 at a trainer) but usually I find there's a reason why horses do things rather than just being naughty.

His body worker said to check him for ulcers. Now when she told me that I had a clinic coming up at my barn so I got some ulcergard and gave him an entire tube for 3 days, followed by 4 days of half a tube. In hopes that it would make him comfortable enough for the clinic. I also had some sucralfate left over from a horse I used to have so gave that to him for a couple weeks. It made absolutely NO difference. 

Am I wrong to think that if it was ulcers, he would have improved at least somewhat? I know the only way to know for sure is a scope but I'm on a tight budget and if my money would be better spent testing other theories I don't want to waste money on an unnecessary scope. I hope that makes sense. Ugh I'm just so frustrated with this situation. He's such a sweet wonderful horse and not knowing what's going on is driving me crazy!

I went through this exact same thing. I scoped my gelding and he had grade 2/3 ulcers. I did 30 days of gastro guard and sucrufate and scoped again. Still had some ulcers at the bottom of the stomach where it moves into the intestines. Another 30 days of gastro guard and sucrufate and he scoped clean. I will also add that I did not ride this horse at all during treatment and left him turned out to be a horse. Even after this horse scoped clean of ulcers, it took him probably two months to relax and learn his belly didn't hurt anymore. Some horses are just way more sensitive than others. 

What do you feed? That is very important for ulcer prevention. I took this horse off grain and will never go back.

I would say you just need to give your treatment more time.

I get this question a lot. For some horses the DePaolo video on detecting ulcers using pressure points is good. I have seen that work a number of times on horses that were then scoped and ulcers found. Scoping only shows gastric ulcers, and a hind gut test may be required.

Once ulcers are confirmed they need to be treated. Usually a thirty day treatment, so your quick trial will not work to find relief. 

At the same time, you need to figure out why the horse has ulcers in the first place, and adjust management to lessen the chance of them returning.

There are a number of reasons they happen. Stress, Diet and temperment can all play a role in the formation of ulcers. Is the horse buddy sour, have limited access to roughage or fed a significant amount of grain based feed? If so, make more roughage available so that there is always something available to eat. Add an alfalfa source to the diet. Greatly reduce or totally eliminate grain from the diet and replace with a higher fat content grain replacer.

I have found that the issue most missed by vets when managing ulcers is teeth condition. If the teeth are not up to date, it can hurt the horse to chew. As a result, they may eat just as much, but only chew enough to swallow due to pain. A horse only makes saliva when they chew, so if they chew less they make less. Saliva is the horses natural buffer for excess stomach acid that can lead to ulcers. 

lots to think about here, but just remember, ulcer control is not as simple as using a few tubes of paste.

Just wanted to answer a few of the points brought up by both of you guys. He is currently living the best life possible I think, especially for an ulcer prone horse. He is turned out on 100 acres with lots of friends, free choice hay, and is fed a 100% grain free forage based high fat diet (he has PSSM-1). 

However last summer he got shipped 3 hours away to the trainer to get started under saddle where he did have free choice hay but was stalled part of the day and in a small paddock with a couple other young horses the rest of the time. He lost weight immediately after arriving and we switched him on to 10lbs of Triple Crown Complete per day (this was before I knew he had PSSM). He did good in training but just could not gain weight and looked terrible so we decided to bring him home after 4 months. 

When he came home I gave him two weeks off and by happenstance that's when I got his AQHA registration results and I found out about the PSSM. So I transitioned his diet, got my hay tested, all that. He started gaining weight immediately but when I started riding him he pretty much right away started having issues with not wanting to go forward. Then the spooking started and is worse under saddle. Then I noticed him biting at his sides after rides and when he was eating.

After making this post I called every vet in my area and they don't do scopes. So he's on a 7 day trial of Gastrogard and I'm probably just going to finish out the full 30 days. Today is day 6 and I haven't seen any changes (haven't ridden yet) but it seems like all the symptoms are there and he just needs more time. 

Another thing to think about is hind gut ulcers. My horse was showing symptoms of ulcers (acting cichy when saddling. So I scoped for ulcers and didn't find any in the foregut. I treated with Succeed for 30 tubes, then switched to the powder on grain.  I haven't rode yet, since its still winter here. But he has gained a bunch of weight all over and looks much better.  I also added Immunbiome supplements Lean Muscle and Spine and Nerve too. 

Also on the scoping, its cheaper to scope than it is to treat if you dont find any ulcers. 

If he is PSSM 1, add liquid vit E. That PSSM causes muscle soreness and that can also be a reason he doesn't want to move. If he is muscle sore that can also cause ulcers because of the stress of being muscle sore. Biting at his sides would make me think ulcers. You diet sounds good though. Your vet can run blood work to check vit E levels. I had a mare with PSSM, after the vit E she started showing progress in about 2 weeks. You have to use the vit E liquid at first, it's what raises vit E levels the quickest. Eventually you can go to powder which is cheaper to keep him in check.

If it is ulcers, the horse starts feeling better around 2 weeks but after a month of treatment should show best with a continued maintenance.