You may have thrush or infection I would get it checked at the dr. it sounds serious. Let the dr. see it one day, I heard when you get peircing in tongues you can get infections alot easier, I would be very careful and see your dr. it sounds like infection or Thrush even adults can get Thrush due certain medications, or viral bug. Good Luck WIth It.
I have the same thing and its also been going on for a while too. Here are some step by step instructions:
1: Starting at the base of your tongue, place a tongue cleaner/scraper flush against your tongue's surface and make slow sweeping strokes from the back to the front. You can start at either side of your tongue and work you way across to the other side. Depending on the tongue cleaner you are using, you might need to make three to four different swaths across your white tongue.
2: Once the surface debris from your tongue has been removed, apply a small bead of toothpaste to the head of your tongue cleaner. Make sure you toothpaste does not contain sodium lauryl sulfate because this ingredient will dry out your mouth (one of the causes for a white tongue). I recommend using therabreath oxygenating toothpaste. (http://www.therabreath.com/product.asp?CAT=3&AFFID=)
3: Gently coat the surface of your tongue (as far back as possible without gagging yourself) with the toothpaste. This allows the toothpaste to penetrate below the surface of your tongue and neutralize those sulfur-producing anaerobic bacteria. Believe it or not, there are more bacteria in the rear of your tongue than in the front.
4: Once your tongue is coated, allow the toothpaste to stay on the surface of your tongue as long as you can. Up to 90 seconds is ideal. If you begin to cough, or your gag reflex kicks in, that's okay, just spit whenever you need to.
5: Ideally, it's best to leave the toothpaste on the surface of your tongue, while you brush your teeth normally.
Following this routine daily gives you the benefit possible in cleaning a white tongue. This routine will help prevent white tongue, keep your breath fresh, and give a geographic white tongue its best possible chance at maintaining the normal, healthy, pink color.
Good luck! I would buy this toothpaste myself, but I really don't have the money...instead I use hydrogen peroxide on my tongue and that does help, but not for long. Also, drink a lot of water. I wouldn't recommend Listerine mouthwash because that can really dry out your mouth.