Dear RB~
Welcome here to the forum, I'm sorry things are as bad as they are.
Toxic means poisonous, something that harms others, eats away self esteem, confidence and hope. You are working in a toxic culture and it is getting to you - as it would to anyone else faced with the same thing.
Many modern companies treat people with any form of illness with respect and go as far as possible to make their lives better, unfortunately you are not in one of those.
So you were a positive person and the same is still inside you, it just needs a better environment to bring it out. Have you given any though to seeking another job - not quitting this one straight away, but looking round for better?
As for being a failure, that is simply not true. When one has a great job it is easy to keep going, when one has a horrible one then perseverance - until you reach your limits - is a sign of strength and determination. You sound as if you are approaching those limits now, so you need to try to get yourself hope.
You may not be able to do all that by yourself, I could not. It took medical help and the support of my partner to improve. So may I ask first are you getting medical support for your depression and anxiety? If not now would be good, if you are then I guess you need to talk to them that under your present circumstances your treatment is not working as well as it should.
Secondly who in your life knows how you feel and cares? I had my wife, who even if she did not know exactly what was in my head tried, and that made a huge difference, I was not alone. So do you confide in your partner?
It can take a surprisingly small change for life to improve, and talking here has been a start - I hope you continue to do so -but talking with oyur medical team (or getting one), talking with a family member or friend, and trying to seek out better employment are all things you can try now -yes I realise it is difficult, almost impossible, I was that way too..
I look forward to hearing from you again.
Croix
