Should i start exercising and eating better?

i'm almost 14 and i'm a girl and if u saw me u wouldn't know that almost all the times that i can i'm eating. and its usually junk food. i'm only about 96 pounds, but my mom said she was like mew hen she was my age and now shes chubbier i guess. so i dont wanna get all fat and gross sop should i start forcing myself to exercise now? because i really dont like to and i'm lazy. in fact i'm hungry now and if my dad wasnt in the other room i would eat Cheez- Its or something. so how should i try and be more healthy? because i know i'm better in the summer cuz i'm swimming a lot.