Outside of the London area, the Benefit Cap allows you to receive benefits including Child Benefit up to £1666.67 per month.
With 4 Children ( if all 4 are included as born before 2 child cap introduced) , if there are no earnings being deducted for on the Universal Credit claim, I am guessing that you received Universal Credit of about £1300* for the month. On top of that you receive Child Benefit. *If you have taken a UC advance and this is being deducted for you will have received less as the advance repayment deduction is part of Benefit cap calculation, when they work out net UC award.
Of course once the Housing rent is paid, you are not left with a huge amount to pay for everything else. What you can do, is ask your local Council Authority for Discretionary Housing Payments as you are affected by Benefit Cap. You can also apply to the Council Authority for Council Tax Benefit. Do this urgently, if not done, as they won't backdate normally.
Your local Council Authority can also offer one-off temporary assistance, if you are in hardship and have no other source of help.
Suggest you seek more Benefit advice and also debt advice, as this may help you organise how deal with the current situation.