You're very young, and showing serious immaturity by thinking of dropping out of university just because you're a little bit older than many other students. Stop being so age-ist! You're supposed to be an adult now, able to get along with people from 4 days to 104 years. Focus on schoolwork.
When you were 8, a year or two difference in age was a big deal due to various physical, emotional, mental development factors. By the time you are 18-21, those differences are less marked. And you are supposed to be an adult, albeit a very young adult, so start acting more maturely. Stop obsessing over age & get to work!