I have been stuttering since the age of six and have received treatment for as a child. I am now 21 and I still stutter. There have been periods where I don't stutter much or at all and periods where I can barely get a word out. This can be caused by mental health. I would personally define my stutter as involuntary ticks which prevent me from finishing a sentence. If you personally feel as if your stutter is involuntary it could be that you've developed one. ​ Regardless, I wouldn't change my stutter even if I had the chance :). If you can visit a GP for free see if you can get refereed to a speech and language therapist and they should be able to advise properly.