Should i be concerned about my weight?

im 15 and im about 65 inches tall and i weigh 119 lbs. im underweight a pretty good much. i look like im about at least 140 lbs. im in great shape also i can run fast and i have pretty good stamina and i can do more pull ups, pushups, crunches, then pretty much anyone i know. i started drinking protein shakes and i eat pretty nutritious im just concerned about me being underweight. any else had this situation.