There's one thing that's really bothering me. Stars have lithium too so technically a celestial object with lithium can be either a brown dwarf or a star. So why isn't this an issue. Im confused. Please Help.

Are you spending time sharpening your logic and understanding underlying relationships? Are you reading on a consistent basis? Daily? Are you able to work out the pressure? There has to be a root cause. Understanding is just as important as endurance so take your time understanding the things you don't. Don't ignore it, explore it.