What are your temps like normally? (hot spot, cold side, ambient temp, and your humidity) This will help us give you some better advice. I'm assuming your lamp is your only source of heat. Is it regulated by a dimmer? If not, you need to get one. I paid about $10 for mine from Home Depot and it helps me keep the temps constant. I wouldn't worry about turning off your lamp. If the temps drop too low, you can put your snake at risk for respiratory infections. You might also invest in an infrared bulb. That way it won't be bright during the night (if the snake is in a bedroom). You can also get a ceramic heat emitter in place of a heat bulb.

Ball pythons really need belly heat, so you might want to consider using the lamp just to raise ambient temperatures and investing in an under the tank heater. Just remember to purchase a thermostat for it because they tend to get too warm on their own and can burn, potentially kill, your snake. Here are a few options for thermostats, starting form the least expensive to the most. But remember, the more expensive ones are much better at maintaining temperature:

http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S
http://www.helixcontrols.com/DBS1000.htm
http://www.reptilebasics.com/ve-100
http://spyderrobotics.com/products/herpstat1Basic.html

It does sound like your snake is going into shed. I would make sure the humidity is around 70%. Now, with a heat lamp, that will be pretty hard to keep since heat lamps suck out the humidity. I would mist several times a day (you don't have to mist her, just the tank) and even place a damp towel over the top of her cage leaving just a small spot for air and the lamp. You can also buy some sphagnum moss and put it under one of her hides and keep it damp. This will raise the humidity in her hide and help her shedding.