Wish my luck

i'm 15 , 204 lb idk height excatly , but i really wanna lose weight but sometimes i eat something screw every thing i've done , i'm like losing 1 pound in two days and gain another in one day , i'm trying to avoid sweets and soda and junk food , and also trying to eat more veggies in my food , wish me luck and if you have any advise me pls say it , thanks.