Is it possible for me to loose 40 pounds in 3 months?

It would be very unhealthy and counterproductive to lose that much weight in such a short amount of time. It is healthy to lose about 2 pounds every week (maybe less). That would mean that you would be losing 8 pounds a month and about 24 pounds on 3 months. Be smart about your weightloss, you don't want to starve yourself because you make your metabolism slow and you are only setting yourself for failure in the long run ( you will crave what you are not eating way more than you do now). Teach your body to gradually reduce portions and substitute candy with fruit. Be more active in ways that are attainable and keep you entertained. Measure your portions and watch out for saturated fats (cheese especially). You are young and you have no excuse to not be active or watch out for your diet. If you have too much time to think about eating get a hobby or join a club (sports groups).