I went through this about two weeks ago and they made me spend the night in the hospital to rule out the heart, which is fine. The PA at the hospital thought it might be my esophagus and reflux or a hiatal hernia.
I called my surgeon's office and met with them and they had me get an upper GI. They saw reflux, I'm a year post-op too and I have no fill in my band and it was still happening. They put me on a medicine to help with the acid production. I forgot what it's called but I'm sure your doctor will probably put you on something similar. So far it's gotten better but even with no fill I'm still pretty restricted but because I never lost weight with the band and am now having this issue I'm having it removed soon. Don't worry that doesn't mean you need to, it's my choice. Hope you feel better soon, Nancy.