Starting Ballet advice please!?

I am 18 years old, 5'11 and 190lbs of pure woman awesomeness lol But in Ballet that combo is pretty much not so awesome... I Love to dance and I really like Ballet I think its so beautiful I started practicing on my own for about a year because I wanted to lose a lil weight before hopping into a leo and tights so I lost 25lbs and I feel ready I know all my Barre excercises and basics but I just dont wanna be the "Tall chubby girl" in class I know alot of the dancers are super tiny and short and I feel like the Jolly green giant! any advice on how to get over this and things I should do for my first Ballet class would be really appreciated!!