The only way to be sure you have 'healed all' is to do a complete fast. This means to fast until you have no stores left and are completely clean inside. The time this takes for a person of healthy weight can vary from 20-30 days to maybe 50-60 or more. In some cases too our stores are not up to the full task of cleaning out and we will regain hunger before the task is complete. But there is never any set time limit. If you went to a fasting retreat you would be assessed and given an estimate. That's a bit beyond us here I think, we can only give estimates based on our research and personal experience, which can't compare to a doctor who has fasted hundreds or thousands of patients successfully.
If you have 'uncomfortable' rather than life threatening complaints, then I'd suggest a fast of 3-4 weeks may be sufficient. But the only way to be sure of complete healing is to fast to completion, either in one go or over a series of shorter fasts with proper refeeding in between.