Diet Help?

ok. im 15. Ive been on a low calorie diet for a month, and ive cut out pop entirely. I drink 8 gles of water a day and my diet contains all the nutrients i need. I havent eaten any junk food. I exericse alot. I run as soon as i get up in the morning and do some more cardio workouts in the afternoon and night. Im not severly overweight though, I just want to lose 10 pounds to get a better figure. Is it true that the less weight you have to lose the harder it is to lose? I just dont understand while im not getting results. Any Advice? Help please.