Hello Angelique67. I don't have phobias but I can understand the discomfort, anxiety/panic you are experiencing. Don't know if this would help but maybe you could try going up and down the stairs on your bum. This is the safe way people with injuries to their legs navigate stairs. This technique may work if your phobia is one of falling down the stairs but may not help if you're phobia is to the stairs themselves.

Wishing you well.