First, stop smoking completely, utterly and "once and for all."
The next thing would be to get an appointment with your doctor as soon as possible, whether it's your regular family doctor or the student health office at your college. This site really isn't the place for diagnosis. At the risk of sounding like a broken record, have a list of all of your symptoms and questions with you when you go in. The more information you have for them, the better an answer you can get.
I don't know if this will ease your mind, but half of my tongue was replaced in 2005 and I speak as well as I ever did. People I've met recently don't know unless I tell them (and I do) and folks I've known forever say they can't tell the difference.
Please let us know how this turns out for you.