I think it’s mostly about confidence and fear of embarrassing yourself. I went through phases in my life where I stuttered more in my primary language, because I felt like I was expected to speak well and fluently whereas with my secondary languages there wasn’t that pressure and even if I stuttered I felt like I could just pass that as me learning the language. If I were you I would think about what it is about English that scares you? Beyond the stuttering. Is it a fear of embarrassing yourself? Being rejected? Fear that it will affect your career or your worth? Once you become aware of that it’ll loosen itself a bit. It helped me a lot in my 4 languages because It was a result of imposter syndrome. Once I worked through that I started having less blocks