Having on & off sharp shooting pain under left breath through shoulder blade, only lasts for split second but i am worried..

Too many possibilities: To give a good answer here. If you are otherwise healthy without other diseases especially lung ones, this may just be some rib irritation or costochondritis. If you are short of breath at rest, or have a fever, get checked. It would not hurt to take ibuprofen or aspirin for the pain. If it keeps up, get examined by a doctor. A physical exam will be helpful to evaluate this problem.