Not put in the contribution esa support group years ago

I worked and contributed to NI for 10 years from 1998-2010 when I had to leave employment due to refractory epilepsy. I was not aware but I was put in the income related esa group. Then later put in the income-related esa support group I was then given a back date of £14,000 because I should have been in the support group before. I am now being investigated for my housing benefit which involves them looking at my bank details. I did not know their was limit of money I could have in my account because I thought I was in the contributions-based esa group. I have too much savings especially since they gave me the back date of money. I am so scared that I will be done for benefits fraud. My epilepsy affects my memory because I have brain damage where memory is stored. What is your advice? I contacted my MP who said they would write a letter. At the same time I am being moved on to universal credit. I have had to delay this.

Hi David,
Yes that does help but I accumulated more money over the years and this would not be a problem if I was initially put in the contributions group which I think I should have been. Have you heard of this happening and the government admitting their mistake so all of my money is protected?
Many thanks
Danielle

Hi David,

The problem is I cannot contribute to receive contributions based ESA because they put me on income relate support group ESA from the beginning. Which they should not have because I had been working for 10 years previously. Does this make sense?
In addition, how do I claim a means test benefit from UC? I have received a migration letter; is that the same? I haven't done it yet because of the investigation - I am so confused
Thanks
Danielle