Hi. I was in the same situation with no friends or family to help out when my second baby was born. In the end DH had to miss the birth to stay home and look after DS.

I would suggest getting out to mothers groups etc with your DD as much as possible just to see other people. As an alternative to a nanny/au pair, you could look at getting a cleaner in - that may be a bit cheaper and will lessen your load.

Good luck