Get in touch with your local volunteer Carers agency or Carers UK itself has a telephone help line.It often helps to talk. Also, just try and keep to a strict routine of doing things-I will do this for 10 mins,15mins etc and eat regularly even if you don't want to. It does ease with time, but that isn't much help at the moment.
CRUSE also is useful-not just for widows!
All Best Wishes,
Bridget Leech exCarer