Will he think im lying?

He shouldn't make you smoke, why does he care if people smoke or not?

Is it that big a deal? Teenagers make such a big deal out of smoking weed

Don't worry about what he thinks and don't be defensive about it. You don't even need to give him [i]any[/i] explanation. The less you explain, the less he will pressure you. Just say you've changed your mind. If you feel you must give an explanation, say, "Bad for my teeth, talked to the dentist about it." Then do not discuss it further. If he keeps on trying to discuss it or tries to make you defensive, ask him, "Why is this such a big deal for you anyway? Why does it matter?" Then let [i]him[/i] explain. You have a right to do what you think best. Stick to it. Remember, any guy who gives you trouble over a decision like this is not worth a lot of time.