I need help pls

hello, I want to start off this postby saying I am 15 in highschool and I made really dumb food s=choices last summer, so now i have a lot of belly fat and overall just dont feel comfortable in my body. I am 5'7 and 138 poundslast summer I was 115 but then I was 5'5 I started my weighloss journey december last year but I have only gained more I know fluctuate from 139 to 142and Im just soo tired of everything since im still a teen I dont really have a say in what I get, like, im broke but i try to go to the gym as often as I can which is about once a week and I try to do pilates too which probably about twice a week iff anyone has some advice it would be much apreciated. I dont want to go back to my original weight but around 119-125 would be fine and I really want the belly fat to be gone. Any and all advice is apreciated.