I block when I’m tensed

I block when I’m tensed Hi guys, I have more of a block rather than a stutter and wanted some advice on it. When I’m talking to myself I can speak fine, however when I’m talking to others my body tenses up (stomach, chest, throat) and this causes me to get out of breathe and block. How do I train myself to stop getting so nervous when I’m talking to people? It’s very frustrating because I think I block because I’m scared to block, and it’s a self-fulfilling prophecy. How can I rid myself of getting tensed up and nervous every time I speak to people?