I'm tired of this character

The situation is a bit complicated, but I am halfway convinced that I suffer from social anxiety. Most of the time, I stutter when speaking to a stranger I am talking to. I also do not prefer to communicate with others, for example, someone would send me to buy something for him from a store or ask him about something. This is from my childhood. I was raised in the wrong way, I think, because I did not meet people much other than those I knew, such as my cousins, family, and others. It was like extreme shyness in addition to constant thinking. I consulted a close friend of mine about this subject. He told me to just trust yourself and not care. I tried and tried until it happened to me twice, I think, as I entered a state of complete comfort and fluency of tongue. I became like a person with a strong personality. However, that state did not last for more than a few hours at school. I went and tried to return to that state and became less thoughtful and had that heart tremor that comes to me when I talk to a stranger or from the class, but I cannot. The situation often ends with me saying something stupid or doing something stupid and I become a laughingstock.