Actually, it isn't impossible to lose 30lbs in about 3 months. You just have to eat healthy, about 1500 calories a day. It really isn't that hard to stop eating junkfood. It's a good idea to lower your intake of junkfood slowly, you'll hardly notice the difference. Pick one day when you can eat something you like, for example ice cream, but don't eat too much of it. And you have to exercise, atleast 30 minutes a day, the best would be about an hour a day. You should do the exercises that you like, like riding your bike, take a walk or maybe swimming. Don't weight yourself everyday, since your weight changes from day to day, about once a week is enough. If you just exercise and eat healthy you're gonna reach your goals.