How do i lose weight? im 13 ....?

ok so i am 154 pounds and i was 138 pounds before i moved out here in the province of ontario. ive went out with a guy who is my age and he is willing to break up with his girl now to go out with me when i go back home in another 10 weeks from now. i didnt want to change when i came out here. ive lost 7 pounds all together in 3 weeks and i am disapointed in that because ive worked so hard and ive ate right and i just cant seem to lose any weight. i think that its just my selfasteam or just that guy who i went out with before. he was my first boyfriend and he used to say i was chubby than. and when he will look at me when im home i think that he will never ever go out with me again. im in kickboxing now and its my last week because i got my blackbelt and im really good at this sport. i do 40 sit ups & 50 push ups when every commercial comes on. but im wondering how do i lose more weight before i go home back to Labrador in 10 more weeks. ? HELP!