I've dealt with depression for many years and I understand the feelings that you are failing everyone. But you're not - it's a chemical imbalance, first of all, so if you don't have your act together, it's not your fault. Secondly, the condition changes how you view things so sometimes (often) your perspective on how you are "failing" or others' reactions is really skewed. So when our kids gripe about what we cooked for dinner or how we're wacko moms, sometimes it's just the kids spewing off and not really anything we did - we just react to it as if we are failures.
Medications have their place but they don't work for everyone. In fact, a recent report (maybe 6 months ago) said that many of these meds work better for people with severe depression, and have minimal effect on those with moderate or mild depression. Sometimes changing them can work, sometimes not. There's a certain amount of experimentation involved but if yours isn't working, it's not working. I needed to change, for example, because my first anti-depressant also had a sedating effect - that might work for some people, particularly with an anxiety component, but it just made me more tired and sleepy, and less able to get anything done, which of course made me feel like dirt. So a change might be in order for you. Don't beat yourself up that you should be grateful for what you have (husband, kids, etc.) - yes, you probably should, but that's not the cause of your depression and you cannot talk yourself out of it by making yourself feel worse!
I agree that a lot of things in our food supply disrupt our bodies - processed foods, even fresh foods picked weeks ago and shipped in a container have a lot fewer nutrients than they did a generation ago when more farming was local and seasonal. I disagree that a particular vitamin will make a difference. Vitamins are not meant to be taken in isolation from other vitamins and minerals and trace elements. Also, pills are absorbed about 17-25% so they are generally a large waste of money.
I do know people who have done elimination diets, but they are complicated and a real nuisance. The problem is not really that we are "allergic" to certain foods but that we lack the necessary tools to process them completely, and the unprocessed or uneliminated portions. As a nutritional consultant over the years, I've learned that adding in a comprehensive formula of balanced nutrients can make all the difference. Not only can people eat the foods they enjoy, but they can reduce their depression. I had phenomenal results and have, with my doctor's cooperation and blessing, reduced my antidepressant meds and I feel much much better with more energy to work out, more clear thinking to accomplish tasks, and more joy in life. I'd be happy to help you too.
But this situation in which you find yourself is not something of your making - it's really a condition that can be corrected in one of several ways, or a combination.