Have you had your thyroid checked and a general health check? I'd do that first, to try to get to the root of the depression and the weight gain? Why do you think you are depressed? Why do you think you've put on so much weight? Do you binge eat? Comfort eat?There are other approaches for eating disorders.
However, there are different types of tablets that you would qualify for - the appetite suppressant type ones such as Rimonabant (side effects in some people include really savage irritation and bad temper and insomnia) or the fat absorbing one - Orlistat - which means you have to stick to a v low fat diet or you will have uncontrollable oily diarrohea. They work, but only marginally - you will lose a few more lbs than would by dieting alone, and if you don't control your diet you won't lose any weight at all (and will have oily orange poo!).
For some people they make a difference, but it's worth remembering they aren't a magic bullet. But I can see you in a position where your health is at risk. You might also qualify for a gastric band or other interventions. It is worth seeing your GP. But all options are pointless unless you can get your eating under control.