Lauru
What to say... when we are depressed we always think the worst... maybe you are making what she said mean things that it really doesn't
I don't know about the not telling her thing, I'm not saying to tell her but having to pretend that everything is alright seems really stressful for you. I tell my partner that I am "a bit down" when things are bad (understatement!!!) it means he knows to go easy on me, or why I am behaving differently etc
Have you got other people to talk to if you can't talk to your partner?

I'm really sorry that you feel like this, I can't imagine how trapped and stressed you feel. Remember that she might NOT leave you even if you go to hospital...
As Shakti says, your illness is lying to you.... it will not always be this way, it will end, it will get better, you are not a failure nor a looser,
YOU ARE A SURVIVOR, YOU ARE STRONG AND CAPABLE