Can't lose weight!

I'm 17 years old and obese. I've been dieting and exercising daily but only gaining weight. I used to be a healthy 130lbs but since taking antidepressants had gained over 50lbs in two months! I stopped taking them a year ago but I just can't seem to lose the weight. I think there may be some sort of chemical imbalance in my stomach, after doing some research, but my parents refuse to take me to the doctor to get me tested. I'm out of options and I really need some help!