Housing Benefit problems

All about money
Any advice would be welcome. Some background: I care for my elderly mother around 15 hrs per week. Same for my dad who does not live with my mum. cannot claim carer's allowance, but can't work either. I have nil income but some capital from a pension I recently cashed in, from which a nominal income is calculated. My mother also gives me some financial support which I declared on my housing benefit claim, even though I didn't have to. I was advised some time ago that all voluntary income from charities and family etc. is disregarded for benefit claims and in the past they have not asked me how much or what it was for, even though I told them how I was supporting myself. However, I have recently been sent a letter from the council benefits office, asking for details of my capital (one full years bank statements), details of how much my mother gives me and what for, and a written statement from her. I told them the truth and have been informed today that, because I have provide care in return for the support my mother gives me, it should be regarded as income, even though she would have given it to me anyway, whether I provided care or not. If this is true, my claim is likely to be recalculated for the last 4 years since I gave up work to help mum and dad. I've just run it through a benefits calculator and it works out that I may have been overpaid housing and council tax benefit to the tune of over £6000. I feel sick. If the benefits calculator is right, should I appeal on the grounds that she would have supported me charitably anyway even if I wasn't providing care? I have spoken to welfare rights and they, surprisingly didn't seem to know how to advise me. I don't know what to do. This will wipe out half my capital and leave me unable to pay my rent and council tax for very long. I'm at a complete loss.
Hi Kairi.

My advice ... seek legal assistance from the CAB :

https://www.citizensadvice.org.uk/

None of us on the forum are legal experts.

As a backup , Shelter are to be recommended :

https://england.shelter.org.uk/housing_advice/benefits