Let me suggest to initially try to cut down on simple carbs. That means fewer processed carbs in the form of sugar, chips, potatoes, bread, and corn. Eat more vegetables and fruit instead of simple carbs and softdrinks.
For some people this makes a huge difference.
It really is going to be best for you to get your body fat lower before you are 20. From my casual unscientific observation, people who are overweight as teenagers tend to suffer from weight problems the rest of their lives. Those who are fit at 18-20 tend to have an easier time. I can think of exceptions, but I think a healthy and varied diet is a habit that you should start building now.