Are you getting therapy for yourself? It might help YOU return to the person you were when the 2 of you were first together. Also, might give you a good outlet for some of these feelings. You can't change her mind, but you can work on changing yourself and that might show her another step you are willing to take to work things out.
It IS stressful to feel helpless when a spouse is depressed, some of what you're saying sounds like you responded with frustration, maybe try to find a healthy outlet for those feelings when they come up?