He said it sounded true and he refused to believe I invented it.
How did it sound true to him? Did you tell him the reason ahead of time?
True-sounding stories are always the most successful. The problem is that they are not always actually true.
Did you tell him something that was untrue? if so then you should clarify it or you'll be dubbed a liar.
He's a liar.
Just because he's lied to you before doesn't make it okay to lie back. You two will just wreck any trust between each other if this continues. Don't you think you're better off if someone stops the cycle of lying?