Well...I know what it's like to have anti-depressants pack on the pounds but, the thing is, the only way you'll know if it actually is the antidepressants is if you keep track of how much you're eating and the exercise you're doing. Honestly, fifteen minutes a day is a good start but the weight isn't going to come off that quickly with only fifteen minutes of light walking and an uncertain diet. Anyhoo, the best thing I could tell you to do is start writing down what you're eating. Calculate the calories, even the food without labels. There are several websites that can help you do this. Another thing I would recommend is adding about a minute each day to your exercise. I've done this in the past and it helped the weight come off faster. As far as the depression goes, been there. Done that. Got the t-shirt. lol It'd be funny if it weren't so sad. The best thing you can do about that is be completely honest with your psychiatrist. Tell him/her if it's not working, your side-effects, all of your concerns. They're there to help you but they can only help if you tell them what's going on.

Apart from that, good luck. If you ever need to talk, I'm here.