Marriage works both ways, or at least is intended too. She is not really there for you, either, it seems. If you have spent a long time caring for her and taking care of her needs and not seeing to YOUR needs properly, that will make you depressed. I am not blowing you off or minimizing. I can tell you hurt and what you most want is to be better, to feel better and feel like you are in control of your life. That is not too much to ask, by the way.
As for being on your own to sort yourself out, you might have something there. (See above) I am concerned that you have set up your marriage and your life around taking care of someone who does not, in turn, take care of you. You are missing reciprocity in your marriage. In my limited observation of life, marriages which lack reciprocity do not work well in the long term. Not everyone has what it takes to give selflessly day after day without breaking under the pressure. You have your own difficulties with anxiety and depression, you need to care of yourself, and you are here feeling worse because you are not there for your wife. Who is there for YOU? You count too. You are worthwhile too and you deserve to have YOUR needs met too.
Be easy on yourself and do see the psychiatrist. If you can go to counseling, please go. I found it extremely helpful and I am sure you would too.
The Lady Dragonfly
Yes, it was me...I know because I was there when I did it. Lupus sufferer, bipolar II sufferer. Currently on Indocin for chronic pericarditis related to lupus, and cherishing every deep breath without pain. Currently in graduate school for mental health counseling, class of Fall 2007. Vegan and loving it!