it may take at least a year or so to clear all of the loose hair and it will all grow back within a months period.
Have your Cav checked for demodectic mange. Mine had it at 2 months... Sixty days of Ivermectin should help. This is also known as "Puppy Mites" and they are not contagious to other animals or humans. My pup lost her ahir on her front legs and head/face area, and paws. She's doing much better now that she is on day 37 of the medication. Her fur is thick and full like my other Cav. Hang in there.... this can also lead to a staph infection, whcih needs to be treated with antibiotics.