Your situation is more than frustrating. I agree with Lefty. From my POV, in the long run, significant weight gain can be just as depressing and dangerous as our mental issues. I would ask for a drug change!

For much of my life, when I eat and do the wrong things (sugar, unhealthy carbs, to much chocolate, don't exercise)--the weight piles on. Though everyone has to figure out their own system, I try to do the following things--early dinner and no food after dinner, no alcohol, meals consist of proteins and vegtables, plain yogurt and a bit of fruit or granola as snacks (but the less snacking the better). My main snack is coffee with whole milk and a splash of H & H. Gave up sodas years ago.

When you want to snack at night--think of how grumpy and stressed out this will make your father and use it as motivation. Though it is harder to sleep when we are hungry, studies show occassionally fasting or not having 3 meals a day is good for us. It can be uncomfortable, but you can get used to it once you get started and continue long enough to make it a habit. Our ancestors did not have food available to them 24/7. You will feel so good about yourself if you can make some positive changes in your diet.