Doctors can you tell me how often should you clean your contact case?

No absolute rules: Contact solutions are a good culture media and the lens and fingers can transfer infectious agents into the case. However, it is hopefully only your case, so any organisms are likely to be ones less likely to self-infect. The frequency in part depend upon your hygiene and also on how frequently you use the case for your lenses. If dirty, then clean with a brush and use alcohol sterilization.