I personally have never contemplated self-harm myself, but I do understand the self-hate you're experiencing. As stutterers, we face challenges in our daily lives that most people would consider trivial, like ordering food or asking a worker in a store where an item is. The anticipation that you'll stutter deters you from taking certain actions, so you avoid the actions, and then you're stricken with feelings of dread and regret for not going through with what you had intended. I know you've probably heard it ad nauseum, but acceptance of your stutter can take you a long way. While stuttering can be greatly improved, the chances of you completely surmounting it in adulthood is near zero. That means you have to work towards being ok with occasionally being embarrassed or else you'll perpetually feel like garbage. From my perspective, it's your mindset more than anything that's holding you back