Don't rely on the diet cookies or any diet food/drink. It likely will just leave you disappointed. Focus on eating meals, not just eating all throughout the day if that's what your trouble is. To lose weight you need to exercise annnnnd eat right in conjunction with each other. Aim for at least 30 minutes a day at first, it can be just walking! Then build up from there. Cardio such as that will slim you down. Depending on your height, weight and age you need to be eating a certain amount of calories. If you continue to go over that number, and aren't exercising enough, you'll gain weight, no doubt.
That being said, don't think of it as something severely strict. Once you get into the pattern of eating healthy meals and exercising even just a bit, you'll start losing weight and it'll be easier. I realize that it's not the easiest thing to do when you feel less than excellent day to day, but as you start eating healthier and exercising, that in turn will actually make you feel better emotionally. Good luck to you!