Why am I suddenly doing this

Why am I suddenly doing this First of all, I’m an 18 year old male and a senior in highschool. Recently I have been stuttering and I have NEVER in my life done this. I will be talking and in the middle of a sentence, for no apparent reason I physically cannot speak. For example at work I was asking a customer at work if they have a rewards account with us, and I could not say the word reward, but could say stuff in between like apologizing for not being able to say it. I’ve also noticed my speech (over the last 6 months or so) is becoming less coherent, slurring words, stuff like that. I feel like I’m going fucking crazy it’s affecting me at work, home, school, and in me social life someone please tell me what’s wrong with me