Hi… Just check ur shoulder movements, whether associated with any pain or not…..if pain is thr means it’s due to shoulder joint issue, if no pain means mostly muscle pain due to abnormal posture while working or sitting. Better do some Neck and shoulder strengthening exercises..k

According to ur age there is no chance to increase ur height Naturally, only way is surgically we can increase ur height up 5cm but it associated with risk and complications.