I wouldn't suggest losing 20 lbs in 60 days. Mathematically speaking, that's 1/3 lb every day which equates to a 1165.5 calorie deficit everyday to lose that weight. I don't think it's possible and I don't think you should strive for that big a loss because it will ultimately result in a gain more than what you started with and that can be a big bummer.
I would suggest start slow and steady to get rid of it and by the time school starts, you should have made enough progress to be noticed and to keep you motivated to continue.
*After re-reading your post, I think you're worried that people will start thinking you've gotten fat. Most people probably haven't even noticed your weight gain since they saw you almost all the time. But they will notice a loss after not seeing you for a couple of months...so keep chugging, it's not as bad as you think!