How fluent would you say your English actually is?

How are you so fluent in English? What is stopping you from becoming fluent in English? I talk to myself in English to become fluent in it. Does doing that makes me weird? Why is it that I can speak English fluently in my mind but when it comes to reality, I can't really speak English? I usually get stuck while speaking in English and find no words to express myself. How do I improve?