Of course. In fact most teenagers at your age go through what is commonly called ‘Body Image Problem’. We do our best to look our best. There is nothing wrong in trying to look good. You should do your best to look good.
What should worry you is actually comparing the way you look with that of others. God has created you the way you are. You are unique and different. That is the beauty of being you. that is God’s gift to you. You are too precious to be copied thus he created just you like you.
If you are in the habit of spending too much time in front of the mirror, you can think of better alternatives. By spending long hours in front of the mirror you would not become more beautiful,anyway. So our suggestion to you is this: next time when you are in front of the mirror just smile and say “you are so beautiful” and get back to something really productive.