What is wrong with my stomach?

I started feeling nauseated every time I ate about 4 years ago. I had a gallbladder ultrasound that didn't show anything, but I had a HIDA scan that showed that I had a poorly functioning gallbladder. My gallbladder was removed, and I started to feel better. Now almost everyday I feel nauseated and don't have an appetite. My stomach hurts in the upper middle region. It feels like the food is pushing back up. My doctor says that I have reflux, but I never have heartburn. I take Nexium 40mg daily. It feels like a bloating or pressure in my upper abdomen. I always have to burp a lot. I have had an upper scope that just showed mild gastritis. I was also diagnosed with IBS before I had my gallbladder taken out. I'm just not sure why my stomach always hurts and I'm always nauseous.