Hi there, I'm Viva and I have bipolar I disorder. I had a good career as a nurse up until the last few years, when my illness got completely out of control and I ended up on Social Security Disability. I was rapid-cycling and meds just couldn't keep up with it. If I'd known then what I know now, I would've gotten diagnosed and treated sooner (I was 53 when diagnosed for the first time), and maybe I'd have been able to rescue my career. It's too late for me, because even though I'm stable I have memory issues and trouble with focus/concentration that are incompatible with nursing. But it doesn't have to be that way for you, and I hope you will be able to continue on.
First thing, if you haven't already, get help! Your current treatment regimen, if you have one, is not adequate. Almost no one who is medicated properly lives at that level of depression and anxiety. I hope you have an excellent psychiatrist (not a GP) who is up on the latest bipolar treatments, as well as a therapist who can help you sort out your fears and feelings of inadequacy. There are also a number of in-person and online support groups; I use the bipolar forum on Psych Central often because they "get" me. Nobody knows MI like the people who live with it day in and day out. Also check with groups such as the National Alliance on Mental Illness (NAMI), Depression and Bipolar Support Association (DBSA) and Mental Health America (MHA); they are good resources not only for sufferers but for their families and friends.
Take care of yourself. Make sleep and rest a priority, eat nutritiously, and exercise if you can. (Personally, that's last on my list because it's impossible when I'm depressed, and I can't channel the extra energy when I'm manic so all I do is pace or bounce my leg, but most people can and should get regular physical activity.)
Be gentle with yourself. There are always going to be days when you cannot meet your own expectations, let alone anyone else's, but that's not a time to get down on yourself. Talk with a counselor or a friend. Do something that makes you happy. Then go back the next day without dragging yesterday's trash with you.
I would caution you against sharing your diagnosis with anyone at work. While some nurses work for progressive employers where MI isn't so stigmatized, the sad fact is that disclosing a mental illness at work is all too often like handing the enemy the ammunition with which to slay you. I've experienced the losses of two jobs where I disclosed my BP to my supervisors, and if I were ever to work someday, I would NEVER do that again. Healthcare people are some of the most judgmental folks I've ever met---not all, by a long shot, but enough to make life as a mentally ill nurse far harder than it has to be.
Anyway, those are a few of my thoughts. I hope other nurses will weigh in here, there are several of us who are open about our MI here on the forum and we try to help as much as we can. All the best to you.