Ask for appointment either with cardiologist or gastroenterologist.
The pattern of your pain resembles heart pain. Heart pain can go along entire left arm toward the small finger. It is related to exercise, stress, cold. Quite reliable diagnosis is by trying nytroglicerine tablets right after the pain. If this helps in few minutes, it's probably heart related.
GERD goes with stomach burning, heartburn, possible burping. Gastric pain is worse after meals, duodenal pain is worse between meals and during the night. Acidic foods and drugs (aspirin, NSAIDs) aggravate GERD pain.