I take lexapro for my mood and depression, ive been on it for 2 months. Ive always always struggled with weight gain, I was only 70lbs when I was 10, so my mom made me gain weight with protien shakes, which got me to a stable 90-95lbs by 11-12 and it was stable until a few months ago when I hit 105 it might be because of puberty (im 13) but I started gaining weight and I know weigh and I now weigh 120, and im concerned because Ive never gained weight this fast, I usually gain 5-10 pounds a year.