I am sorry you are feeling badly. I hope the venlafaxine helps your mood.

I have only one child and had difficulty caring for him when my depression was at its worst; it must be very difficult to be mom to four. I don't have much advice but I'd say do the most important stuff and let the little things go. Hug each child and tell them you love them. So what if they miss a few baths or their clothes are mismatched or not tidy. I read a book once that talked about "good enough mothering". Kids don't require perfect moms to grow up okay. Love them, feed them. Snuggle with them in bed if you can.

Keep posting and I hope you feel better soon.