Hello. There is little background information, so my best is a projection of my own experience.
Stuttering is normal, but if it often interferes with your speech, you need to practice. Especially if the language is not your native one: any deviation of the interlocutor from your prediction of verbal and non-verbal communication (people who are afraid to talk or are inept often do this - how to approach, what to do, etc.) can knock you out and prevent you from formulating a response. Stress is noticeable, even if it seems that everything is under control.
I don't quite understand what is meant by “never say what I mean”.
Are you unable to express your thoughts concisely? Or do you get anxious and start rushing and say things that others find offensive?
If the first is the case, practice writing your stream of thoughts on paper in full and then abbreviating it on another sheet of paper.
If it's the latter, try slowing down to find the right words. With experience, there will be fewer mistakes.
You should also expand your vocabulary by reading books, listening to podcasts, etc.
Try to practice your communication with people you don't like or dislike (remember to be safe and polite) - you'll feel more confident. As a rule, it is easier to communicate with people you don't care about than with those who are “above” them in your mind. At the same time, you will realize that a significant part of people are indifferent (in a good way).
You can also practice in front of a mirror.
If you're in a small town, not a metropolis, you shouldn't go out and “shout”: there can be consequences, and if you don't understand why you're doing it, no one will understand you, and you won't understand yourself either.
Consultation with a speech therapist idk but we call them logopedist.
Have a nice day!