I had a stutter in kindergarten, worked on it, then as I got older It came back in college when I was about your age. Had it all through college and went and got an mri after college then saw a neurologist. He told me that the stresses of being an adult can bring the stutter back from early childhood. It sucks but you gotta play the hand that was dealt to you. Furthermore if it’s sudden/severe you should see someone and get it checked out. Could mean neurological issues.