You poor thing. Remember you will get the baby bonus, and depending on income you will also get some money from Centrelink. I don't know your full story but can you go to the bank and talk to them? Sometimes they offer pregnant pause (i think it is called) where you pay interest only instead of the full mortgage repayment? How long have you had your mortgage for? Can you re finance it if you have enough equity?
Can you have a garage sale to get rid of things you don't need to give you extra cash to get ahead? Also if you have annual leave you could get that paid to you when you go on maternity leave.
good luck, I hope others will chip in and give you suggestions.