Student or Learner
"My illness recovered."
"My illness healed."
"I am recovering from my illness."
"I have recovered my illness."
"I have been recovering from my illness for the last nine months."
Can illness here be replaced by sickness?
Healing happens to a person or an animal, or sometimes, metaphorically, to a device. An illness can go into remission, and people will often say things like my cold got better although logically, it was the person, not the cold, who got better.
I am not a teacher.
I think Tarheel's response was supposed to draw our attention to the fact that the fourth sentence in the original list is not natural, in addition to the first two.
When I first read post #1, I thought sentence four read "I have recovered from my illness". I think Piscean probably read it the same way. We sometimes see what we expect to see.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.