Can any1 please help?have tried ringing for the past 4 days and can't get through, any advice would be appreciated?

Hi, I have received a letter from from hmrc dated 8th July 2013 saying that I had been overpaid £1394.76 in child tax credits. I will start from the beginning ... my boyfriend had been made unemployed back on the 24th February 2013, I wrote a letter to hmrc the next day explaining my boyfriend had lost his job and sent it away, thinking that they would adjust my benefits accordingly as that is their job :{ I never received any communication from them until my tax renewal pack came through and I sent it away. My benefits never changed, I was still receiving child tax credit but never thought anything of it as I had told them of my boyfriends Change of circumstances and thought I was entitled to it. In the meantime, my boyfriend got another job and started on the 6th of May, I wrote a letter to hmrc again informing them of his new job and sent it away..or so I thought I had, my gran had died in between this time and I was quite depressed and only found the letter I was supposed to send away 2 days ago!!!I know that you have up to a month to declare a change in circumstances and its obviously past that now, what can I do? I also don't understand why I have been overpaid in child tax credits when I sent the letter away to declare him losing his job, they have obviously received it now as I have the letter stating that I have been overpaid?I don't know if my letter was lost in the post and delivered late. I didn't keep . A copy of the letter, the only proof I have is that I date all my letters when I write them which will probably count for nothing to make matters worse my 3 year old son is in private nursery and starts going to full days in August, he gets sop many free hours a week but it still adds up to £245a a month and that's including funding from my local council. I can't get a place for him in a normal nursery as there are no spaces and I don't want to disturb him as he has settled in there so well. Hmrc have stopped all my payments and I currently get nothing except £20 child benefit so I am stuck with , an expensive nursery fee each month, rent, gas , electric, food it's just not practical!I currently have £2 to my name and my partner has £30 after we have paid everything. We both also have debt which we are trying to pay and we have had to cancel making payments for now which means interest will start to pile on again. I don't no what to do. I work 16 hours a week and make £500 a month and my partner works 40 hours a week earning £989 a month, between rent, nursery fees and gas and electric, council tax, food, we are left with nothing I'm starting to get too stressed where I can't eat. Any advice would be appreciated?