I need to lose all of my lazy weight

So on the last few weeks of senior year I got busy and didn't have time to make food or workout. I gained a lot of weight and I miss my old body and my flat stomach. Now that summer is here I've got use to just grabbing the first thing I find to eat and vein lazy. Any tips to lose weight fast. I've tried working out but nothing is happening and I'm trying to eat healthier but it's not doing anything. I need help. Please. I wanna feel confident in a swim suit again