OP, you are not alone. Far from it. I could have written your post, for our experiences parallel each other's even though my diagnosis is bipolar 1 with anxiety. I've never lasted at a job more than 2 1/2 years, and the two longest-lasting jobs ended in my having a breakdown. I am also the sole breadwinner for my husband and myself, yet I've taken huge risks by impulsively quitting jobs because I couldn't handle the stress.
I know what you mean about being a good nurse. That doesn't necessarily translate to being a good employee, which in nursing usually means submitting to being overworked, dealing with bad management, not getting breaks, and generally being treated like a pack animal. Working in such conditions naturally contributes to stress and burnout---even in nurses who don't suffer from mental illness---and for people like us, it can be disastrous.
Obviously, working as a nurse is a trigger for your depression and anxiety. It can be overcome, but medications aren't enough. I know your finances are tight, so you may want to consider checking out your local public health clinic; they usually have low-cost mental health services that charge fees based on income. The major disadvantage here is that you may not see the same psychiatrist or therapist every time, but it's a lot better than nothing.
You can also see if your own pdoc will work with you by temporarily reducing his fees until you're back on your feet. Mine carried me for eight months while I was uninsured, for which I will always bless him. The worst thing that can happen is a "No", but you'll never know unless you ask.
In the meantime, you may want to think about a lower-stress nursing job such as doing admissions for a SNF or working part-time as a flu clinic nurse. Neither is particularly exciting nor well-paid, but they can put food on your table while you sort out your options. I had to leave clinical nursing entirely when I realized that I could no longer handle it either physically or mentally; now I'm a state surveyor of LTC facilities, which brings a lot of stress with it as well, but it's different stress---I'm not holding anyone's life in my hands while coping with the inevitable ups and downs of my illness.
Once again, you are not alone. Many nurses have walked in your shoes, and we know it's hell. I hope a few more will weigh in here, as there are a number of us who suffer from depression and anxiety and can share some wisdom.