I need to lose weight before prom

Kate
So I'm 17 almost 18, 5'10, and today I found out that I'm almost 200 pounds (192.6 to be exact). Which is something I personally never want to be. My boyfriend says I'm not fat, my friend says I'm not fat, but I feel and look really fat. So I was wondering if you guys have any ideas how I can drop 50 pounds before prom in April/ May. Keeping in mind that yes I do have a job but I also am working for my car and college please nothing costly. Also I am about to go gluten free since I seem to have a reaction to gluten.