Seems to be quite a normal phenomenon amongst stutterers. I had a similar experience as well, I basically overcame my childhood stutter until the age of 16 or so when I moved to a new high school. Out of nowhere it came back like a freight train and I still stutter about the same as when it came back at the age of 26. I feel your pain, just don’t let the reemergence of your stutter cripple your confidence. Just remain composed and get the words out even if you stutter a lot more than usual, that’s all you can do.