The foods you like aren’t necessarily bad. The key is moderation.
Eat chicken just roasted, not fried or with fatty sauces. Potatoes are not fattening if you don’t put sour cream, cheese, and things like that all over them, and very healthy if you eat the skins, too. Yogurt is a great thing to eat on a diet. I would go for low fat or nonfat yogurt, plain or flavored with fruit only. If you can’t find yogurt flavored with fruit only, get plain yogurt and add fruit to it yourself. That’s a good way to ease fruit into your diet, and it also eliminates a good deal of sugar. Most flavored yogurts on the market have lots of sugar (check the label, it will be about the first ingredient), or else artificial sweetener, which isn’t very good for you either.
Macaroni and bread are not at all bad to have in your diet, especially if you switch to whole grain versions. If they’re made with white flour, there’s a lot of straight up starch. If they’re all whole grain, they have lots more nutrients, and they’ll help you feel full for longer.
To introduce vegetables into your diet, get a vegetarian cookbook or two (you might be able to borrow them from the library if you can’t or don’t want to buy them at this point) and follow some recipes. Vegetarian recipes tend to do things with vegetables that the typical meat eater never thinks of. They’re great ways to make vegetables tasty even to picky eaters.
Finally, don’t push yourself to lose 20 pounds in just two months. The most weight it’s safe to lose is two pounds a week, which would be up to 16 pounds in two months. More, and you’ll be pushing yourself into starvation mode, which will make it much harder to keep the weight off and more likely that you’ll have trouble losing weight in the future. If you really do need to lose 20 pounds (not knowing your height or build, it’s impossible to say how far your current weight is from your healthy one), you will after you adopt healthier eating and exercise habits, even if it takes a little longer than you prefer.