Sharp back pain around/under left shoulder, going through my chest when taking deep breaths. Worrisome?

Possibly. The symptoms don't sound like something that is life or limb threatening. However, I am sure you are in a lot of pain. The cause may be a herniated disc, something that doctors don't often think of when evaluating someone with back and chest pain. If you do seek medical attention, ask you doctor if he/she thinks an spinal MRI would be helpful.
Seek help. This could be musculoskeletal or it may be cardiac in nature for example. See you internist and than follow up with your orthopaedic surgeon if symptoms persist.