Your best bet is to arrange an appointment at your local job centre or even just call them they will be able to tell you what your entitled to. I think you might be entitled to a carers alowance and your child tax credits might increase too. Im not very hot on what your entitled to as im not claiming everything i should be... Good luck coping alone. If you need a chat come along and have a moan... i frequently do it. x
I'm assuming you've let the tax credit people know that you're now a lone parent? Depending on your income and rent/mortgage, you might want to look into whether you're eligible for Housing Benefit and Council Tax Benefit? I still receive some even though I'm working 40 hours per week in a fairly well paid job (simply because cost of renting in London is ridiculously high!)
I don't know much about Carers' Allowance or other things you could be entitled to.