Very unlikely, however arent you also afraid of lung cancer? or second hand smoke to your child... Just a thought you're 19 let this scare get you on the healthy lifestyle path.... No smoking, drinking, etc........ wish I knew then what I know now... this scare should show you s**t happens and you cant take it back...
Hepatitis C is spread blood to blood, so it would be extremely unlikely that anyone could get it by sharing a cigarette unless the cigarette had blood on it, and even then probably not. In fact, I believe the transmission rate from needle stick accidents in hospitals -- where there is blood transfer - is only around 3%. That said, you can always get tested if it's on your mind but certainly would not lose any sleep over it. What you don't want to do is share personal items -- like razors, nail files, etc -- with someone who has Hepatitis C.
So don't worry and congratulations with your baby son.
-- Jim