Not quite sure on your circumstances but if you live with a partner married or not and he works then you can get child tax credit and depending on income working tax credit. Also dependent on income you might be able to get council tax and housing benefit. You'll also get child benefit which is a bit of a pittance.
If you're living together and not working then you can get income support/job seekers allowance alongside child benefit. You'll also get a premium on income support for having a child.
However if you're NOT living together then you are a single parent and will get income support plus the child premium, single parent premium, housing and council tax benefit, child benefit but the CSA will pursue your partner as you are claiming benefits whether you're in a relationship or not.
If you've worked and are pregnant but not entitled to SMP then if you satisfy the working conditions of 26 weeks out of the last 66 (I think) then you can claim maternity allowance for up to 26 weeks if your baby is due before 1st april or 39 weeks if youre due after 1st april.
Sods law I'm due before