Suddenly developed stuttering

I like to start by saying that I was a completely healthy child. In fact, I was the quiet,calm and well-behaved kid that every parent wishes for. I did great in school, never had any problems concentrating or finishing a task. I've mentioned all of that to accent the fact that i never had any behavioral\psychological disorders, and still don't.
Currently, I'm 22 and in uni, healthy as a bull, don't take any medications, except for the occasional paracetamol and herb based pill that eases sleep (only took it 2 times). Didn't have a stroke, head injury or any traumatic experiences. Don't suffer from anxiety, depression or any other disorder that comes with suddenly realizing that life is not as beautiful as we used to think as kids\ higher education\ton of responsibilities.
Recently, by that I mean half a year or so (can't say exactly) I've noticed that I have difficulty pronouncing certain syllables\sounds. It can be in the beginning of a sentance, or in the middle of it. For example if a word ends in a certain way and the next one starts in a certain troublesome syllable. When a word like that comes up, I tend to pause for as long as 10 sec (never counted-just a guess) close my eyes (if my many attempts at pronouncing it are futile) and try to force myself to pronounce it. Sometimes,even clench a fist or two. Also, if I know beforhand that I'm gonna use a word with the problematic syllable, I try to think of replacement, or even try to change the entire sentance.
I didn't pay any attention to the so called problem since I thought that maybe my thoughts are too fast for my mouth to keep up with, as funny as that may sound. I also thought that it can't be stuttering, since I always thought that stuttering is only repeating certain syllables\sounds. I discovered that it might actually be stuttering when I started researching it after watching a video of an adult doing that. To my utter surprise, I understood that my difficulty is indeed discribed as stuttering (according to some websites).
I've also noticed that I stutter most when speaking with family\close friends, which rules out nervousness or\and social anxiety. But maybe being an introvert and holding long meanigful conversation only with people I truly know, has something to do with it.
I'm fluent in 4 languages, and stutter in 3 of them since I have no one to speak English to\ no need in it.
Anybody experienced something like that? any thoughts on what may have caused that? Is this really stuttering? any opinions\views are appreciated.
P.S- even when I speak normally\slowly I have this problem.
Sorry for any grammatical errors, I've tried my best. English is not my first language.

What I've meant to write is :"Suddenly developted a stutter". Can't edit the post and this error is killing me.

I can sit in my own room with no one there and I still can't say the word I'm trying to say at that very moment. It's not often at all, but it's there. I hate it. But I've been this way since a tiny little girl.

Just a thought, do you stutter in your native language? Or just in languages you have learned which are not naturally used?