HELP MEEE PLEASEEEEEE,!?

Okay, so I'm leaving for vacation down south in April. I wanna loose about ten pounds, fifteen would be nice but my parents say it's unhealthy since I would look like a twig, I'm about 135 pounds right now, How can i shed the weight off? I try, I eat super healthy, but nothing seems to work. Breakfast is usually peant er on rye toast, water throughout the day, for lunch = 1/2 cup all bran cereal with 1/2 cup skim milk then some gs, then whatever my parents make for dinner. I CAN'T LOOSE IT THOUGH! I'm not fat, but i'm not skinny either, i'm like average, but i 'd like to flatten my stomach and get rid of my jiggling fat. UGH! lol, i'm sixteen and a girl, i'm five foot two and a half. What can i do? Please help? Also, it's hard to always faithfully eat healthy, especially with friends and my boyfriend and family eating whatever they want and me always being around.