As one person living despite depression (which is how it feels sometimes) to another, hang in there. I've recently been showing low on the tests (which surprised me, since I don't actually feel any different from me at my worst) and my shrink is encouraging me to get out there and Do Things again.
I think getting past the whole "I'm worthless" thing is something which takes a long time. Being together with your Person, however, is probably going to be a fair bit of help there - I doubt they're willing to listen to you putting yourself down without attempting to contradict you. Me, I'm finding after nearly twenty years of continuously hearing (in so many different ways) that I *am* worthwhile from Himself, it's a lot easier to get past the nasty bits of my brain which try to tell me I'm not. So my suggestion there is to listen to their opinion of you, and ignore your depression-brain's opinion (you're allowed to be wrong - and one of the things you're allowed to be wrongest on is your negative opinion of yourself).
But it is possible to live with depression, or despite it, and actually have a pretty good life, overall.