My tongue and lips feel numb after using magic mouthwash?

They're supposed to. Magic mouthwash often contains Lidocaine which is a local anesthetic or numbing agent. It also contains dyphenhydramine which can cause numbing. Magic mouthwash is supposed to make your mouth feel numb to lessen the pain of the oral lesion or sore in your mouth.
Try pediatric formul. Pediatric formula may work better.