My dermatologist prescribed a 2.5% hydrocortioe cream for my perioral dermititis, but I'm scared it will make it worse? Any suggestions?

You need to trust. the doctors you see. Perioral dermatitis can be treated with steroids but can also be caused by steroids. If you trust the dermatologist you saw then follow the directions and if not better in a couple weeks go back.
Will help. Another approach is topical metro gel which can be used by itself or incomvition with the 2.5 hydrocortisone, e if persistent low dose Doxycycline is useful in some cases which have small cysts.