Okay, i really want to loose Alot of weight...but the thing is its too hard fo me. I tried 3 times and failed.

okay i weigh 128.6 pounds. Im 5ft 5 inches. Im 16. Im over the average according to my doctor. So i tried loosing weight. I tried 3 times. I lost bout 4 pounds in a month which is not much. All i did was eating really nothing but Breakfast lucnch and dinner. But then i gained and gained. then i went to virginia. I gained bout 7 pounds there but when i came back i went back to 128. I am trying rite now but its too hard. I cant resist not eating. Like if there is a doughnut no1 one wants ill eat it even if im full. I dont know how i can help myself control it and i dont know a rite way to do so. Please help me