Weight Loss Before Boyfriends Grad

I'm currently a junior in high school, I'm 5'7" and around 180 ish pounds. I don't look super overweight but I feel like I'm disgusting. I'm going to be my boyfriends grad escort but I really want to loose some weight before. He says that I'm beautiful and sexy, etc. but I don't want to look how I do now for his graduation.... Some tips and tricks for weight loss would be amazing and I'd be very grateful for the help.