Killer words

What can kill a relationship? 
They are what you use everyday. 
We were talking normally as usual
But somehow, he didn't like the way I put certain things.
He deemed it as a 'demand', when I don't even meant it that way. 
It's so stressful to be with him. 
Every word I said is being judge upon.
Every actions of mine is being judge. 
Stress level: Maximum
When he doesn't like the way I say things, 
He'll use words to hurt me too. 
Why's that so? 
I don't see myself ever getting married 
Or even close. 
Its judgement everyday for me.
I've to be very careful not to make a mistake.
I've to not let him do anything for me
Because he will only expect something in return. 
Maybe it's time this relationship stop. 
But how do I do it?