Well, at 14 your muscles are still growing and deveoping. That doesnt mean that you dont have power now or that you wont have power until then though. Alot of boxers have trouble "sitting" down into their punches. Make sure when you are throwing your straight right, that your knees are slightly bent, and that you are throwing from the shoulder/chin area, and not from the hip. WHen your throwing your hooks and uppercuts, rotate your hips into the punch for more power. Your power will come with time and training, but right now the most important thing to learn is correct form. Train hard and learn all you can from your coach. Eat right and drink lots of water. ALso make sure you get plenty of sleep to keep your muscles well rested and give them time to heal.