Try to start sentences with words that don't give you blocks, like if the word "my" makes you block as you said, start the sentence with "so my" or "okay my" or something. Something that makes me block is my name, so I try to start sentences with "My first name is \_\_\_\_". This helps me a lot. Also, practicing reading out loud constantly throughout the day has helped me build more confidence in my voice. If I'm on reddit, I'll actually read posts and comments out loud.