About couple weeks into new job i started getting a sharp stabbing pain in low back left side. gets worse when i sit hurts to get up and move.?

New onset back pain: If the pain has been there for several weeks you should see a good primary care provider to have a full history taken and a good physical examination. At that point a rational diagnostic and therapeutic treatment plan can be developed. May be something as simple as office ergonomics to something much more serious. If the pain has been there for a "couple weeks" then you should be seen and examined.

Musculoskeletal: The answer is not necessarily an easy one to reach without more info. Does your new job involve a different level of physical activity? Are you sitting in a different position at a desk or computer? It seems like the pain you describe is due to an injury to a muscle or the use of different muscles in your new job.