Hi Margaret,
Do remember that if you are on IB you will be assessed for ESA, you won't simply have your benefit stopped. Even if you can't get IB you are likly to be eligible for Jobseekers Allowance.
Carers allowance may well be a possibility, but you do need to get advice first as your getting carers allowance might affect your mother's benefits.
People on SDA will be assessed using the work capability assessment at some point in the future.
Good luck,
Steve
Nothing on this board constitutes legal advice - always consult a professional about specific problems