Think about applying for PIP - the new version of DLA.
https://www.gov.uk/pip/overview
I am 99% sure it is not counted as 'income' so won't affect your husband's pension credit.
Apply any way, you have a firm diagnosis of fibromyalgia which is recognised as being disabling. I strongly suggest you make an appointment with a specialist at your local Citizens' Advice Bureau and get help to fill in the very long forms. They know how to word it right so you will be more likely to succeed with your claim.
Good luck!