I know how you feel, I’m 28 now & been stuttering my whole life. It was always really bad when I was younger and in high school I remember the bullies old & young they’ll never go away there will always be some dickhead out there. Best thing for you to do is gain some confidence In yourself weather that be in the gym, sports, or anything that you enjoy that benefits you physically & emotionally. Second is ALOT of practice best way to practice your speech is to read poems/ books outloud preferably to someone. If you wanna start just by yourself that’s fine too but eventually build up to reading out loud to someone you’ll notice change in your speech & your confidence. I hope it goes well for you, you have a whole community behide you I’m sure anyone of us will be happy to hear you out.