Ok,
Here are some things I reccomend.
1) Fill the tank with fake plants. You can get a long vine type plant at any dollar store for $1. Fake plants help keep up the humidity, because you can mist them. They collect the water, the water evaporates and makes the humidity in the tank higher, and does not soak your bedding which can lead to scale rot. All in all, a necessary addition for any glass tank.
2) Add a more water! If you have one water dish, I suggest using a short tupper ware dish. Place it on top of any hide so that it is close to your heat lamp. This will allow the heat from the lamp to evaporate the water in the dish, keeping the humidity up. Get another water dish out. It can be any material, plastic, glass, whatever it is put it on the cool side of your tank. Having these two will also keep the humidity up.
3) Dampen a kitchen towel and lay it over the top of the tank. Fold back an area so your lamp can freely project light into the tank. Keeping this towel damp will become annoying, but it's the price you have to pay.
4) If you are willing to spend a few dollars, I suggest you skip the last suggestion and tin foil treat your mesh top. This helps stabilize your tank tremendously. I admit it does not look pleasing, but it makes taking care of your snake alot easier.
Go here to see the tutorial :
http://www.ball-pythons.net/forums/s...highlight=foil
All these should help you get your humidity to stabilize and make it easier on you and your snake. Let me know how things work out.