Ugh. I feel you. Only because I remember with my first two kids, and now I will be you in just a few days (nursing two). It is so hard, but honestly, it *does* help to vent and complain just like you did do. My best friend IRL and I love to complain about hard things with our kids because we know that although it is hard, we are doing the right things.
So I am going to tell you: you can do it! Try to de-stress whenever you can: a bath, takeout pizza, watch TV all day.
While you are sitting (or stopped, at least) nursing, plan the activities you need to do next. Oh, also I just remembered that it will be warmer soon, and that will help a lot in terms of being able to go out more.
My kids are sick right now, and this is just a hellish day. Jacqueline, I think this is the most unhelpful post I have ever written, but I had to respond. You are doing great, and I do think the change in weather will help -- it is all that is keeping me holding on!

Another tip: I have a fantasy project that I "work" on as sort of a treat when I can't get up. I am trying to find some fabric to make some bedroom accessories and drapes and all that. So, when I have to sit down, I just search and search for the perfect fabric. I browse ravelry for interesting patterns, I check out mothering.com (of course!).
Also, this:

a confession: I wish I could nurse my two big kids right now because they are so sick! At least my younger boy will get to nurse his illness away in a few short days when I have my baby!