sharp pain, nasty taste in mouth and always gassy?

Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the sharp pain on left side of abdomen radiating to back. You have also made a mention of probably water brash and dyspepsia.
The pain in your case could be due to acid peptic disease and upper GI endoscopy could be helpful in reaching a diagnosis for the same.
Other possibilities to be ruled out include Gall bladder disease and pancreatitis. If the pain persists, it is wise to go for ultrasound scan of the upper abdomen to rule out these serious causes.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.