I mistakenly deleted some very important messages on my iPhone how do I retrieve them cos I’m not sure I backed up

The deleted messages are deleted, in general.. If you had iCloud enabled for messages, then the messages are gone. If you did not have iCloud enabled for messages and did have a backup from prior to the deletion, and if you are willing to revert everything and the entire contents of your iPhone to the pre-delete backup, then you might get the messages back. But with no backups locally or in iCloud, there’s nothing to revert to and the deleted messages are deleted.