My left shoulder hurts a bit after standing for a while. its been like this for a while. i also noticed my spine is not completely centered (been this way since childhood). could this be due to poor posture?

Maybe/not: Scoliosis is a condition where the vertebrae that make up the spine do not form in a straight line. Like a stack of bricks on uneven mortar, the stack can drift one way or the other. This would be evident on x-ray & most cases are mild with few if any symptoms. It might be posture or poor physical conditioning. Your doc could sort it out.