What do you suggest i do to finally get rid of the extra weight?

Hi I am a seventeen year old girl and I'm 5''2. I was a relatively toddler until i reached age 6, then i started getting chubby. From age 9-13 i was overweight (kinda fat after 11) . At age fourteen i drastically decreased what i ate and lost some weight but that i was unhealthy and i just went from being fat to chubby again. At age fourteen and a half i started to lose weight again, in a healthy way that time. I did five months of that and then i stopped trying to lose wight but i kept losing ( i kept watching what i ate though). Then at 15 i would walk and at times jog about 4 miles every morning (rarely jog) , i walked everywhere i went and i walked at least a couple hours wherever i went, i went to waltz cles 3-4 times a week in the afternoons, and i ate whatever i wanted: junk food, soda, candy, 6 tacos every night (just that summer), and i was losing weight! i got to weigh 118-120 lbs. I as so happy but then i returned to the U.S, and school, andi gained again. Ive been struggling to lose the weight, even though I've tried. Right now i way 143 lbs, and im trying to get back to the 120 weight. I have a history of overweight on my moms side. What do you suggest i do to lose those 20 lbs before summer ends? ( if you have any tips on how to keep it off i'll appreciate it).