I don’t know how to be myself

I (16) feel like a different version of myself when I interact with others. I am not very talkative, and I don’t know how to start a new conversation. I’m constantly careful about what I say incase it is affects me or others in the future. I don’t like telling people about myself. I have never trusted anyone. I struggle to truly like people because I think that people dislike others by default. I don’t know how to be myself.