Hi!
I agree, If Dr is concerned I wouldn't worry myself too much. Chickenpox is only contagious till blisters come out. So your son is no longer contagious. Avoid scabs and liquid from blisters coming into contact as this can sometimes have active virus therefore be contagious. Try to isolate all contact such as kissing, towell sharing, bedding etc.
HTH and good luck for the birth.