I hope this doesn’t sound like we’re ganging up on you hear but sit down and have think back to that time. There’s bound to be something that’s triggered it. Could be something really small too. Therapy could be an idea if it’s maybe a suppressed memory you’ve not dealt with. Speech therapy is also a good idea. It doesn’t work for everyone so don’t be disheartened if it doesn’t. It’s worth a try though because you never know. You’re still young so do as much as you can to socialize. I never did this and I’ve struggled for quite a while talking to new people. Make a good habit out of it and it will help you with anxiety in the long run. Practice speaking at home. Read books out loud. Talk to your parents more. Finally, and most importantly… accept and embrace your stutter. It’s not going to go away, you’re only going to get better at masking it. The quicker you accept it and stop caring, the easier everything gets. I’m 22M, had a stutter since I started talking. I’ve only started to accept mine last year. Life is slowly getting better. The person who cares most about your stutter is you. If you embarrass yourself in front of someone, remember that they will forget about it straight away. Good luck and I hope you find your own techniques soon!