witter are you still watching as you've gone quiet and this is turning into a debate 
As you are a single mum you ought to be getting Tax Credits at the lone parent rate which (from past experience) is vastly more than the normal element. Ditto for Child Benefit (for the time being!) I'm sure that if you are also working less than 16 hours per week you can claim some financial support (if your income is THAT low). Also bear in mind that when lo arrives these benefits will increase substantially...so if you could just get the absolute essentials for now and make do until lo arrives and get the rest?! Argos have a moses for £25 atm. You can hire a Kari-Me sling from most SureStart CC's for £5...and they are amazing for carrying baby PAIN FREE for a LONNNGGG time!
If you wish to go out to work then certainly childcare for your son should not be the only reason not to! You, as a single mum, are entitled to around 80% of the cost of childcare covered. So for every £100 of childcare costs - you only pay £20.
I managed to work my backside off as a single mum of 2 children (self employed childminder). And IME I was actually better off financially as a working single mum! Now I'm married to DH & expecting Dc4 things can really be a struggle as we both work and get sod all!! 
If you are truly struggling to purchase extra bits for new lo, then contact Jobcentre Plus about the Discretionary Social Fund (info on pg 160 of the pregnancy book midwives issue).
But my concern would be that getting another job whilst highly pg will be both exhausting, short lived and damn hard with a bump! 
Also what date are you due in April? Are you 100% certain you don't scrape into the last few ppl who are still entitled?
And a long shot...are you not entitled to Maternity Allowance???
You mention that you were working before & that you only claimed Income support late last year??
As long as you have worked for ANY of the 26 weeks in the 66 weeks (which should take you back to around the beginning of 2010) before your baby is due you can claim...this includes periods of self employment!! AND FINALLY...there is Employment & Support Allowance! If I were you I'd make sure you have exhausted all avenues.
I also second the other posters suggestion that you contact the CSA as soon as possible as from your post it sounds like your partner is still working? Well cop him for 15% of his net earnings for one child....20% for 2!! Personally I'd nail his goolies wallet to the wall for not supporting you!
. I know first hand how CRAP they can be but 5 phonecalls a day soon gets them in gear!
And finally a personal rant...I do wish people would stick to the subject in hand and not turn it into a debate i.e. FF/BF debate! It is personal choice and there actually IS strong evidence that BF babies are LESS likely (not that they NEVER) to suffer certain illnesses in comparison to FF babies. I can actually see the the other posters were merely trying to offer sound advice on a way to feed OPs baby which is FREE considering her post is about financial issues!! Also can I just say...bed sharing and co-sleeping with your baby is NOT unsafe PROVIDED it is done CORRECTLY. In fact NHS staff advocate it to promote successful BF but there are strict contra-indications & guidelines we must adhere to. Ask your community midwife to advise you if you are unsure. The fact remains that this post is not about the feeding debate or any other issue. Sorry but it esp makes me
when inaccurate info is posted. Sorry. 
Good luck and i'm sure you'll get through it...women just have a way of coping! Please let us know how you get on. X