OK cool. Don't be concerned. Puberty late onset things are common. Especially in the mouth area. A feeling of your jaw locking is a very common one, but that's bone growth not in synch. Let me give you some advice, you already know it's there so you can keep on top of it. Slow your speech down a little bit, breathe a bit more. Try to connect your words to make them one long sound. Don't force anything, if it sticks and you force it then your brain will go into a panic mode and it will make it worse. Stay calm, breathe through it. At the very, very worst, you may have a stutter. But that's not the end of the world. We are all here for you and nothing holds us back either. I, personally have my inbox open to anybody who wants to talk. If that worst possible scenario happens, you're still good. I hope that helps in any way.