Laura, let me preface all comments with "I am not a medical doctor and do not play one on the internet." So, when in doubt, consult with your medical advisers who are qualified!
With that caveat... all I can say is put one foot in front of the other, and set goals you can meet.
The big goal is to create habits that are strong enough to carry you through mood swings. So build them slow and steady, until they're totally automatic.
If you aren't exercising, you might consider starting - there's a lot of evidence that it helps depression. If so, begin at low enough levels that you can be successful, even if it feels puny at first.
An analogy that changed my thinking about setting goals... if you started weightlifting, and planned to lift 100 lbs the first day but could only manage 50, you wouldn't say "oh, I'll do 150 tomorrow to make up for it." That's so obviously idiotic. However, many of us (including me) say similar things with other types of goals, and don't recognize that it's equally idiotic. "I meant to read four articles, but only got through two. I'll read six tomorrow." As if! Pretty soon the pile-up of the un-doable becomes overwhelming, so I quit completely.... I'm learning that I have to start with the bar low enough that I can succeed, and raise it from there.
And so do you. So be gentle with yourself. (My new mantra.)
Best wishes.