What you don't do, that you need to do, is ASK FOR HELP. Most sane women would have asked a friend to help with that birthday party, given your stage of pregnancy. If you don't have these kinds of friendships, you need to make developing them a priority. You have a mindset that you can do it all yourself (including driving yourself home from the hospital after giving birth, how crazy is that??) and you don't avail yourself of the help that is out there.
Time to start developing your network and letting people help you out. I bet you'll be surprised at how willing people are to help a poor pregnant lady