It's hard to say without really seeing your baby, but it doesn't particularly sound like reflux to me based on what you've said. It still could be and maybe I'm just not seeing the full picture. All 3 of my kids had reflux, and while there is a wide range of symptoms, mine all spit up A LOT, and not just right after meals, but even an hour or two later. They also were more than just uncomfortable - they would scream and were in real pain. None of them ever really had a "normal baby" cry - more screaming than crying. Also, arching of the back during or after feeding is a big reflux sign. If you think you may be dealing with reflux, I'd be happy to share some of my experiences with you.
As for the formula, ideally a gradual switch from breastmilk to formula may have been easier (unless your son was having the same issues on breastmilk), but if you couldn't do that don't worry. Just move forward from here. With the reflux, we did have to try out different formulas, and we were told by our GI doc that it can take up to 2 weeks for a baby to start adjusting to a different food. If it's tolerable, maybe stick it out a few more days and see if things start to improve. If it's not tolerable, then call the ped and ask what they would suggest you try, but again be willing to give your son a bit of time to get used to the new formula. It's possible you may need to try a few before you find one that works, but just don't switch too frequently or you may make it more difficult for your son to adjust and might even miss one that would work for him.
Hang in there. It can be exhausting and frustrating when something we think of as simple (eating) turns out to be a challenge. Try to be patient and work with your doc and I'm sure you'll find the right formula for your son.