My Doctor Prescribed Prilosec 20 Mg Daily After He Did

My doctor prescribed Prilosec 20 mg daily after he did an endoscopy that showed Barrett's esophagitis. He prescribed the medication for 6 month period and then I'm scheduled to have another endoscopy. I have been taking Prilosec for 3 weeks and I have acid reflex, bloating, mild gas pains and I can't sleep lying down. I always feel like I have to belch but I can't?