At 14 years of age, you shouldn't need to worry about this. This should be the least of your worries. Boys often hit puberty by the age of 14 and ends usually several years later (around 17 years of age).
With that being said, if you are that concerned about your height, stop eating the junk food and eat more healthy. Now, this won't necessarily make you any taller than what you are, but it is better for the body to keep it healthy.