Hi Rayne-- I feel ya! Take a deep breath (that always helps) and I'll give you my 2 cents worth. I'm also BP2 and have been symptomatic for 43 years.
You're stressed and tired and frustrated and confused. You're also worrying about issues way beyond whether or not to change majors.
The thing you have to decide is whether to finish your degree in psychology or change majors. My advice would be to focus on that decision, and let the rest be. Things have a way of working out, and life's always full of twists and turns, even for folks w/o mental illness. And you can't make that decision effectively in the headspace you're in now, so talk to people and keep posting here. Your school should have a free counseling program for undergrads.
If you do change majors you'll be a lot more employable in the short run. Consider these factors: you want a job you can enjoy and feel fulfilled in. If child development or nursing would supply that, it's all to the good. Secondly, if you get a degree in one of those you can always go to grad school and work on a Masters in psych later. Finally (and most obviously) changing majors means joining the work force sooner rather than later.
Work. I've never been able to hold a job longer than 4 years, so keep that in mind.

I was most successful teaching high school, because it was rewarding and structured. The structure really helped with being able to work. I taught for about 11 years altogether, with two breaks in between.
The financial cost of graduate school is considerable. I was in grad school from 94 to 99, didn't finish my PhD, and am WAY sunk with debt from student loans. If you can get a TA-ship or outside work, it would be a lot easier financially.
Grad school was pretty enjoyable for me, but then I've always loved teaching and learning. My symptoms were minimal during grad school, which was nice. The main thing to remember about grad school is that it's very stressful and very time consuming. But I'd say it's also very worthwhile if you want the advanced degree and concomitant employment possibilities.
Now take another deep breath.

I know everything's crazy for you right now, but this too shall pass. Focus on one thing at a time, and realize that whichever decision you make it won't be the end of the world. Believe me on that one!
I hope my ramblings are at least somewhat helpful. I empathize with your situation and am sending positive energy your way.
all the best,
Randy