Most girls are not fully developed at 14. Your figure will come just maintain a healthy lifestyle and remember everyone is shaped differently. For example, my mom has a thin athletic figure with a small chest. I'm curvy, carry more muscle and kinda busty. Remember not to compare yourself with others too much because every healthy body is different and beautiful. I've been teaching middle school for nearly a decade and can guarantee you'll look different in a few years.
Depending on your height you probably don't need to lose weight. Try toning your muscles; that might help define your figure, but you're body isn't fully developed, so be patient; all good things come in their own time.