Alex how about you look at things another way.
You are 14, you have at present lots of hair, it is a little curly which when wet is allowing you to see your scalp. It you had shorter hair this would be less noticable.
Use a good shampoo and conditioner, you dont need to be 18 to use those and they can give more volume. There are sites for hair loss that sell shampoos that have very weak dht blockers in them like saw palmetto, pumpkin seeds etc.
Then when your 18 you can start on topicals if you are still feeling that you want to.