heartburn responds to antacids but has been chronic for 11 years

I have had chronic heartburn since my pregnancy 11 years ago.  At that time, my ob/gyn suggested Pepcid AC, which I took a few times.  I have mostly relied on Rolaids all these years, but the heartburn occurs frequently enough that I generally take 10 to 12 regular strength tablets in any 24-hour period.  My internist recently suggested Prilosec OTC, which helps with the heartburn but causes side effects of terrible gas (and I have read that it can lead to osteoporosis when used long-term).  So I am back to Rolaids.  I like the taste and have no problem taking them throughout the day, but am worried that I am at risk for Esophageal Cancer.  My question is:  if the heartburn goes away for 1-2 hours or more when I take one Rolaid tablet, does this mean that I do not have chronic heartburn?  Or should I undergo an endoscopy to determine whether or not I have Barrett's Esophagus, hiatal hernia, etc. ?  All these years, I have naively thought there was no major GERD problem b/c my heartburn goes away when I take Rolaids -- at least for several hours.  Any guidelines about how to define chronic GERD?  Advice about how to proceed?  I am 42.