If you haven't already, I hope you will get your heart checked out to rule out coronary artery disease... even though you aren't too worried, you won't want to wait too long on this and possibly suffer a heart attack because you didn't get it checked out in time. Hopefully, they will want to do a nuclear medicine stress test (if they feel your heart is up to it) to rule out a cause for chronic chest pain. Any kind of pain, if bad enough, I believe can make a person feel nauseated.
I know nausea can be a symptom of gastroesophageal reflux disease (GERD), but you say they did an upper endoscopy, which showed you were okay... were there no signs of GERD (acid reflux damage) then? If no signs were seen, why do they think an acid reducer is going to help you? Have they considered and ruled out a gastoparesis (delayed gastric emptying) issue as the cause of your nausea?
Another thing- has anyone looked at your gallbladder/duct system and how well it is functioning to try to rule out a gallbladder/bile duct problem as the cause of your nausea? Is the chest pain more toward the upper right? If so, please ask for at least an abdominal ultrasound to look at the gallbladder, liver, pancreas and bile duct system. Better still, I was told sometimes a HIDA scan (you would want it with ejection fraction to see how well the gallbladder is working) can show what an ultrasound misses. I've seen examples (but I don't think they are common) on medhelp of people whose tests came back without giving any real concern to the doctor and when they wound up getting gallbladder surgery due to really bad symptoms, it turned out they had a bunch of gallstones.