When i turned over i got a stabbing pulsing pain behind my left breast could it be gastritis? i've had gastritis pain for 2 yrs but never scopped yet

Possible: While it could be related to your gastritis, could be a number of other things and would need physical exam to identify exact cause. With twisting movements that cause pain, could also be related to rib dysfunction, intercostal nerve/muscle irritation, costochondritis, or just a simple muscle twinge. Depending on pain and other symptoms, pain on left side should always be cleared for cardiac issue.