I think what happened is that you originally may have been speaking quietly because of being shy. And then when somebody asked you to speak louder, it felt out of your comfort zone and speaking louder and more powerfully conflicted with your established shy, quiet personality. And hearing that you speak too quietly probably hurt your self esteem because you may have started to question whether you are weaker, or different than other people. And that coupled with the fact that someone misunderstood you as a person who stutters, you became afraid that you might start stuttering and this caused you again to hold yourself back while speaking. You became focused on the wrong things while socializing. You probably became focused on safety/ not being judged, and fluency, opposed to connecting with others and being yourself. I’m not sure but I would recommend that you truly do learn to speak louder, more powerfully, and more assertively. It’s time for you to leave your quiet speaking personality behind and the stuttering is just a good cue to do that. You need to release your inner strength and become someone that is either fearless or doesn’t stop speaking or doing anything even if they feel fear. Before you started stuttering, did you have a tendency to second-guess yourself while speaking? And not talking because of fear of saying something wrong? Are you afraid of telling people no when they ask you for help or invite you to hang out? This may not make much sense to you but I am glad to recommend a few inexpensive resources if these questions apply to you