Any ideas what this could be?

I am 34 years old and overweight. I do not smoke or drink. I have high blood pressure and take Lisinopril and Atenlol for it. For several months I have been having a lot of indigestion. However, it sits in my chest over the left side. I also have some pain in my shoulder and back, and occassionally it causes me to have some numbness. After taking an antacid and belching it goes away. However, I have 2 - 4 bouts of this a day. Usually right after meals but, sometimes even in the a.m. after waking up. The doctor put me on Zantac but, it doesn't seem to be working. I've been told it could be Magnesium deficiency and I've started taking a 250 mg tablet per day. This helps some but, it's still happening. If anyone can provide me with some good useful information I would GREATLY appreciate it and give a best answer.

Also, when I get the indigestion in my chest area it causes some pressure and discomfort. My heart sometimes flutters and it lasts for several minutes to a few hours until I am able to relieve the gas. I have had an EKG and a chest x-ray both of which were normal.