Did this start after going on medication for depression? It may be if you did and are on antidepressants that they are at least partly responsible for weight gain. If that's the cause, the only solution, not an easy one, is tapering off and trying a different one. If no meds involved, then if depression is the culprit depression is what you need to work on. It's like drug addiction or PTSD -- many if not most who have these problems had depression first, though it is not usually known to the person. If they don't solve the depression, it's very hard to make the changes to solve the other problems. But this isn't really hard to figure out, it's just very hard for people to change when they get into ruts -- go back to doing what you were doing 6 years ago when you didn't have the added weight. If you change your metabolism by burning more energy and consuming more reasonable amounts of food and switch to healthful balance of food, the weight should slowly come off and stay off. But again, depressed people find it very hard to make changes -- we become afraid to make changes. So don't be disgusted with yourself, understand yourself and find a good therapist if you don't have one already and start working on regaining the life you let slide when grief overwhelmed you. Peace.
I agree with Paxiled... if an antidepressant is involved, that may be the cause (or partially) of your weight gain. If there is no medication involved, and it's all because of the depression, then finding ways to deal with that would be the first order of business.
We, often have a tendency to be hardest on ourselves when we gain weight and can't/don't lose it but we need to learn to love ourselves no matter what we look like. We're the same person inside, even though the body looks different.
I agree that one of the first steps would be to find a good counselor/therapist to help with the depression and to help change your self image and self esteem.
Take care and good luck. We're here to help you in any way we can.