If I’m correct (someone please correct me if I’m not) I believe people have been known to develop speech impediments cause of things like really bad anxiety or other things of that nature. I was born with my stutter so I’ve had mine all my life but I didn’t even realize I had one until I was in like 7th or 8th grade. That might be what’s happening here unless you’re older than about 20 then I don’t know what the specific cause could be, but I hope you find out the cause of it. And don’t let anyone get you down because of it, it’s not something you can control. I’ve been made fun of because of my stutter for as long as I can remember having it, ignore whoever makes fun of you cause they don’t understand.