How can I support my wife during her pregnancy when I can't even take care of myself?

We have a 1 year old, and my wife is a stay at home mom and is doing so much with him and taking care of him 24/7, and we have another one on the way.

I've been going through severe depression for the past year, and didn't realize it. I was diagnosed finally in July and since then it has gotten a lot better with exercise and therapy.

But this last week has been hard because we finally got to go on vacation as a family. The vacation part of it went great, but when we got home yesterday we were both so exhausted that I reverted to my old ways of thinking and reacting.

I also haven't exercised at all in the past few days.

And just now we had a huge fight because I interpreted something she said as if she was saying I was an incompetent father.

And she just had a panic attack because she feels like she already has a baby to take care of, and she can't take care of me too and now there's this new one on the way and she can't handle all of this.

And the whole time I'm sitting here thinking, shit, she's right. I'm a HUGE fucking burden on her when I should be her partner. I should be someone SHE can lean on, especially now, but instead I'm weak and fragile and worthless.

I feel like she would be better off without me.