The rules and where i went wrong

Don't take any of this personally. It really has nothing to do with you. Your partner's depression is coloring his perceptions of everything, including you and your relationship. If you keep this in mind, you're more likely to hold onto your own sanity.

Well I took everything personally so this was crap from the start

You have to keep your own needs in mind. It's probably a good idea for you to get into short-term therapy to deal with the frustration and anger that you might feel in dealing with your partner's depression.
My biggest fault, I care and I want others to be ok, generally putting them before me

Recognize that any "out of the blue" decision to end the relationship is probably due to the depression. Your partner is either thinking that you'd be better off without her, or is just hopeless overall about the success of anything, including your relationship. Encourage her to put any major decisions on hold while she's depressed.
Not sure about this one, it wasn't necessarily out of the blue and it was needed

If your partner is not resistant to the idea of seeing a doctor, but hasn't gone ahead and made an appointment, then you should take the initiative. The lethargy that accompanies depression could keep your partner from moving forward on treatment.
There was little resistance but i think i put too much hope on the doctor making everything ok

Don't cross the line between caretaking and enabling. Continually putting your partner's needs before your own will not do either one of you any good.
I crossed that line and had no one to help me, there was a degree of jealousy that I wasn't getting looked after but Rach was

Your partner may display jealousy for the first time in your relationship. Jealously comes from poor self image, and depression is destroying your partner's self-image, even if it was always healthy before.
It was there and I'm not sure I realised what was behind it.

Don't feel guilty. Don't feel like a failure. Again, this has nothing to do with you.
Catholics are not the only people who feel guilty, I can't help but feel i have failed to help her, failed to make the relationship work, failed to be the person she needed and not the person I think she needed.