The Past 2 Weeks I Have Had A Bubbly Feeling

The past 2 weeks i have had a bubbly feeling in my stomach after eating. No pain, just discomfort. It is up high near my chest area. I have been taking some magnesium and calcium, plus started Nexium 4 days ago. I've never had heartburn or acid reflux before, so I have a hard time thinking that may be the problem. Went to my doctor and had an EKG, it showed an eratic heartbeat when it gets uncomfortable, but not much else.