It sounds to me like your vocal cords or maybe your bronichial tubes are irritated, possibly from your sinus infection. I'm happy to read that you are using a neti-pot, this will help flush irritants from your sinus cavity. I'd suggest you try squeezing a couple of fresh lemons and bring the juice to a boil along with a couple of tablespoons of honey. Let cook to room temperature and take a tablespoon a couple of times a day. This should help relieve the irritation in your throat.
I'd also suggest if you smoke to try to at least cut down. If you don't smoke try to figure out what is irritating your throat. Try not to laugh so hard until you notice some relief. Laughing until you start coughing is only going to keep your vocal cords from healing.
