My weight is driving me insane! Gaining no matter what I do? Help?

I just turned 18, so I don't know if that has anything to do with it (metabolism slowed down?), but I keep gaining weight for no reason. I count calories everyday, and eat anywhere between 1200-1600 calories depending on how much exercise I do. I didn't overeat these past few days, but I went from 115 pounds to 119 pounds in a week. I'm extremely frustrated because I have been doing 30 min- one hour of exercise everyday and eating healthier. I'm 5'4 and would like to be 112 pounds. I'm doing my best to avoid turning into a "whale", but it's happening no matter what and for absolutely no reason. I used to be perfect weight-wise, but now I'm disgusting. Sometimes I don't even want to go out in public because I fear that others will view me as fat. Any advice? I'm extremely depressed because of this. Thanks
My weight is driving me insane! Gaining no matter what I do? Help?
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