English is kind of my second language. I recently moved to an English speaking country and my native friends have told me my spoken English is fine and is without an accent. However I know my English articulation is limited. How do I improve or expand my vocabulary?

When I'm very engaged I speak without being aware of my grammar/language and it's fine. However other times I'm often conscious of it and as a result becomes a self fulfilling prophecy and speak like I'm autistic.