It seems my advisor doesn't trust me, but why?
You may be misinterpreting and actually getting it backwards. Of course, I don't know the prof or the other interactions, but much of what you write here could well be explained by your advisor trusting you completely to get it right and the other student needing more help and practice to get up to where you are. 

Student X may need all the help they can get, whereas you are trusted to make it without the need for extra intervention. It could also be that some people know you already have enough to do. 

I could be wrong, of course. 

But it would be worth having a face to face conversation asking your advisor for advice on your progress and, especially, any advice on what to do to position yourself for a great career. I'll guess that if there are any reservations about you that they would become obvious in such a conversation without having to directly ask whether you are trusted or not. And if you are trusted, the advice would probably be pretty valuable in the future.