Smoking can do a lot of harm, but it won't cause hair to grow on your face or chest, it won't cause your hair to turn gray, and it won't cause your bones to pop. If you're only a month away from being 18 and you feel this bad, you need to see a doctor. Do you take medications for the seizures?
The facial and chest hair are genetic. It's nothing to worry about. Smoking doesn't age you in this way. It ages you in other ways. It blocks oxygen from every part of your body. Your brain, skin, eyes, internal organs, etc.
If you can quit, do it now. I did it about 3 months ago and I smoked for over 30 years, 2-3 packs a day. I'm lucky that it didn't have any permanent affects on me, but if you're feeling like you're 70 already, then the smoking may be affecting you a lot faster. It's different for everyone.
I've even heard of people getting lung cancer from just a few years of smoking. Why take the chance? My sister already has emphysemia. She can barely walk from one end of her house to the other without being out of breath. She feels and looks 20 years older than what she is. That's why I say don't take the chance. You don't know how quickly the smoking will cause damage. Quit now.
In answer to your question. No, I've never seen or even heard of an 18 year old looking old by smoking. It could certainly make you
feel old though. You should be feeling like a million bucks at your age. See a doctor. Oh, and quit smoking.