I'm also 17, male and have stuttered since I started talking.I also get frustrated when they tell me slow down.Espencially my mom used to tell me this and even yell at me for not talking fluently and always said that the problem is in my mind.I always got mad but didn't say a thing until I couldn't take it anymore and started yelling at her and dared to speak like that to me again and since then hasn't said a thing. I know that it said that if it doesn't go away in childhood it will never will, but I've heard stories that it has even when they were like 23 and overcome it so nothing is impossible.My stutter is mild but is better than before so I still have hope that I will overcome it, in fact I know that I will overcome it.I decided that I don't wanna live with a stutter anymore and i will do anything about that.For my past experinces every time that I have REALLY wanted a thing I have gotten it so I'm sure this time will be the same.So don't loose HOPE.Don't spend free time doing nothing spend it finding a solution for your stuttering.I know there are a lot of pessimists who think overcoming stuttering after childhood is impossible but I fucking refuse to believe that and ONE DAY I WILL PROVE THEM WRONG.