At first calm down bro and it's totally curable bro I am 18, I am about 98 to 100 percent fluent in any pressure its been about 8 weeks since I had a mental block, I worked as a telecaller in my internship so that helped me lot and even as a front desk by be communicating more and more, now for exercise practise breathing speak in exhale and main thing is strech your word while saying eg dependent I couldnt say this word fleuntly and what I used to was like saying it deeependent by saying many times my muscle memory started to think this word is safe now I hardly stutter and at last what I can say is slow down speak in slow pace and combine my exercises for 6 months you will thank me bro and I am sure all the best bro