I was a single mum for a year, my (must get round to the divorce.....) 'ex' husband left 2 months after my daughter's 1st birthday.
Some mistakes I made were:
* not realising the child tax credits were going into his bank account
* being told by the job centre that I was elligible for incapacity benefit for my depression and fibro etc, but I never got any payments and didn't realise so I lost out there
* not asking for more help where it was needed
And I don't remember much else, thanks to the breakdown I had (hub left because we became pregnant again and he hadn't wanted one, let alone some, and didn't love me, and couldn't cope anymore - then that xmas I lost my baby and it was the last straw on the camel's back, so I just lost it over a number of months).
I do miss being the one in charge of her food, activities, tucking her in every night - the reason I don't do these things is I had to ask him to take her and be a single dad while I got help and he decided he likes having her fulltime. But my current partner and I are expecting end of may/beginning of june, and it's irritating having to decide everything for the baby, with someone else! But i honestly don't know how I'd cope on my own again, I've no friends in Wales.
Make sure you apply for any maternity grants for equipment etc, healthy start vouchers will be available when yer claiming from the jobcentre and have your tax credits coming in and blah... Healthy start voucher forms are got through yer health visitor/midwife. When baby's born, there will be child benefit. Being on benefit sucks, imho, but without it, you go without - bigtime. So apply for everything you might be eligible for!
Good luck, it's not the end of the world, I've got single friends in the UK who are doing it alone and doing brilliantly
(and to the mum who posted what her ex has said re the baby being 'out', what a prick, better off without him, hun!)