I just want to add to try to help but because I understand your worries too.
2006 I fell pregnant with DS1 and I was only 21 at the time, both myself and OH were both in uni full time. DS1 was not planned at all and this was my worry too. We had rent to pay on the student house and decided to move in with his parents. We both gave up uni and he got a part time job. I gave up work totally.
Great! You may think. It wasnt so easy though. We still had to pay board to his parents. (£80 a week) and still get all our own food, mobile phone bills, contact lenses, all the baby stuff etc etc. Yes we had a roof over our heads, but OH was on £8000 a year. Definately NOT a decent wage, and coz I had given up uni and had given up my little part time uni job when i fell pregnant, I wasnt entitled to ANY SMP or anything. All I got was the £500 surestart grant. :/
I didnt think we could afford a baby, but we struggled through.
I applied for IS (£45 a week) and when baby was 6 months old I decided to get a full time job so we could look at getting a mortgage rather than renting.
We had been on housing list too and kept applying every week as well as going through mortgage process, just in case.
It is much easier once baby is born as the housing will probably shoot you to the top of the housing list as you would need a 2 bed and if you cant afford to rent privately, that is probably your best bet, or, try applying for a mortgage within your budget now rather than when you leave your job to go on maternity. A mortgage could work out cheaper for you in the long run? rather than dead money renting, although you would of course need a way to get hold of a deposit. :/
But also, dont worry too much as you should be entitled to working tax credits and child tax credits which also helped us massively once we had DS1 as well as child benefit too.
Hope this helps, and Im sure you will figure it out, and try not to worry too much. :)