Hey Christina! Good for you starting to take control of your health at such a young age. I've been dieting on and off since I was 15 (almost six years now), and I think here you have some fantastic support to help you do this the "right" way. Do you have a particular plan you were going to follow in terms of eating/activity? Either way, I'm sure you'll do great!
EDIT: Sorry, I just noticed you mentioned WW. That's actually the first program I tried too. It stopped working for other reasons for me and the reason I went on it in the beginning was my mum had success on it post-pregnancy. Good luck!