I need tips on a for sure weight loss diet.?

I'm 5'9" and it has been awhile since I had been on the scale. It runs in the gene pool to get unwanted fat areas, I don't want that. I find myself constantly covering up my arms and my stomach when I am around my friends because they are thin. I'm not terribly fat, I'm not even fat. But I do feel way to self-conscious and swim suit season is close and I am like ewww. I used to be like a super twig, then I got older and my metabolism slowed. I find myself always feeling hungry and saying I can lose it later. And I think it's time later come. I feel like a fat blob, and constantly trying to compare myself to fat people and I feel awful for it. My clothes are shrinking and I need help!!!