you poor thing, the feelings of nausea are rotten. I've had those physical manifestations of stress/depression before and it is really hard. It's a shame you can't try the St John's Wort, I do find it very helpful. have you spoken to your GP about these feelings?
it's good that you have a friend you can talk to, although it does sound like her way of approaching the depression thing doesn't quite fit with yours. I wonder whether it would be worth considering counselling, or have you already tried that?
hope you had a good time with your family anyway. Interesting that you get along better when there are more people around. are you "home alone" with the kids a lot during the week?
I do think a lot of this is linked to your sleep deprivation too though, I am much worse when the kids have me awake during the night/up early, and of course am useless at getting to bed early myself!
i've been burning a lot of lavender oil lately, just to try to keep a calm edge on things. Not sure if it helps but at least it makes me feel like I am doing something to try to manage things positively.
You are not on your own, remember that.