Hi 7yearsdrained,
You're in exactly the right place. Welcome to the coparenting board! A lot of members here suffer from depression, both clinical and situational is my guess. My therapist told me the other day that depression is often the other side of anxiety, which is a form of imagination. It's strange to think of anxiety as a form of imagination, but it is when you think about it. Your future feels uncertain, you have a sense of dread that things aren't going to go well, or be easy, and so you imagine the worst. Depressing! I'm glad your sister is in your life, supporting you and believing in you. And the economy appears to be picking up and gas prices are low, at least in the US.
You're in the darkest, deepest hardest part right now, and it might feel like everything is going to always be this way. But it won't. Going for a walk when you feel shut down is actually an excellent idea.
You probably won't get back to the old you, the way you were before you met your SO. My experience is that you can actually get even better. You're motivated to support your D5, and that can be an amazing journey. It got me to the best place I've ever been. I had to ask myself what it meant to raise an emotionally healthy child when one parent was mentally ill, and that took me to places that were both painful and healing.
N/BPDx turned out to be my greatest teacher. Never in a million years did I ever think I would say that when I was in the darkness years ago.