GERD; Lightheadedness; Could it be an ulcer?

I have been diagnosed with GERD. I have also had Rt shoulder pain along my scapula. I am scheduled for an EGD because my doctor thinks I may have an ulcer. I have been having severe stomach pain especially when my stomach is empty. Recently I started to get lightheaded. Could this be a stomach ulcer or something related to my gallbladder? Thanks.