I had a lot of trouble expressing myself. Most of the time, at least for me, it was that I literally didn't have enough language to my disposal. I started reading a lot (a lot) and doing crossword puzzles. Boy that was hard. It took forever before I could finish my first puzzle. But it tremendously helped because you're starting to see how other people put their thoughts and feelings into words. Especially things like metaphors, antonyms, etc are hard. But it's stuff you can learn and become good at.
Can this be related with stuttering too?
Seems like my spouse also has this pattern - not enough language, which leads to stuttering.
I think it's because he feels pressured to speak english fluently (he is non english native, and people usually even subconciously look down on people who cant speak english).
Like you said, not enough language. He said that if in his mother tongue, if one word doesnt come out, he can always find another word because he has vast vocabulary on his mother tongue language. But in a foreign environment and language, he doesnt have enough language, he only knows that word. So he doesnt have any other choice other than using that word, even though the word doesnt come out from his mouth. Which leads to the need to repeat from beginning and stuttering, under the pressure.
Usually people are kind enough to wait for him, but this stuttering caused his confidence level to drop. So the anxiety/depression cycle continues..
When he is less anxious, he can do much better.
Hopefully like you said, it can be learnt and overcome. I do think if we learn more about the language, phrases, and vocab, it will get better. But it still depends on the person, whether he is willing/ready to face the problem and endure the pressure of learning (especially together with other people in a language class) or not.
Willingness to learn is very important, but it may be hard for some people with restricted interest and difficulty in adapting with new (lessons) environment.