You may have opted into the "Hide my email" setting when logging in with Apple, which generates a random @privaterelay.appleid.com email address that won't be linked to your original email address.
While it might look strange. you should continue using your Apple login. Otherwise, logging in with other methods tied to your original email will create a separate account on Shipt.
To regain access to your old Shipt account, use one of your previous methods to log in.