If you had a peptic ulcer, otherwise known as a stomach ulcer, the pain would be on the LEFT side, since that is where your stomach is.
Also, nausea from ulcers is often relieved by eating food; it doesn't get worse. Plus, you have been taking medications that would normally calm down the pain from ulcers.
The gallbladder is on the right side. However, when you normally have a gallbladder attack, it comes on suddenly, with excruciating pain. The pain is usually felt in the back also, although it is possible to feel some pain in the front.
It could possibly be your gallbladder; but it could also be your liver. That would explain the nausea after eating as well as the pain. It would also be in the upper right side of your abdomen.
The bottom line is that there can be a number of problems. You need to see a doctor & tell him/her what is going on. GI problems can become very serious is left untreated. So, do not try to self-medicate any longer, and get yourself to a doctor.
I hope you feel better fast & that it's not too serious.
I have ulcer disease & I have had my gallbladder removed. I have liver disease & gastro-esophageal reflux disease. So, I have had a lot of GI problems.