I also started stuttering a year or so ago, never having stuttered in my life. It got so bad earlier this year that I was admitted to hospital as they thought maybe I'd had a stroke. I couldn't speak properly at all, and I was slurring, trying to get my words out. They did MRI and CAT scans, among other tests, looking for a neurological reason for the sudden speech problems. They found no signs of stroke, tumours, etc, thankfully. As I do not take drugs or any medications, it was not a symptom of that either. My stutter is psychogenic. Unfortunately, that's where the care ended, and I'm dealing with it myself whilst I wait for speech therapy. Ask your GP to refer you for tests and go from there.