Hi, I'm 16 and I plan on becoming a veterinarian as well, although I'm a little closer to it than you are since I'm older. Make sure you keep your grades really high and work hard because vet school isn't easy!:) It looks like you are having fun with your horse and that is really what matters right now. Good luck in the future and with your dream.
Wish I could see the picture, but my computer at school blocks a lot of the pictures:/
There is nothing wrong with a dream like that!
To help you come out of your shell, you should start taking lessons with a group of riders your age. Maybe join a drill team! When I started on my drill team, I was around 14 and the most shy person around. Being on the drill team help me bond with my horse, trust my horse and fellow riders, and I am now the most outgoing person on the entire team. I'd even say it helped me with my barrels, since it gave me more opportunities to ride in rodeos. I've gotten "Class Clown" 5 years in a row:)