I got my ball python over labor day weekend (about a month ago) and feed her(assumed gender) one thawed fuzzy every four days. She has only defecated once since I got her but she still has 7 mice inside her. She is still very eager to eat so I'm assuming that she knows best but I'm still concerned. Another thing I'm concerned about is that fact that she hasn't shed yet. I checked the sheet that was give to me when I bought her and she hadn't shed when she was at the store either (the got her July 24th, 2012). Since I've had her, I've noticed a small dry patch on the top of her head. She's had it since I got her but it's slowly spreading but about 1-2 scales a week. Does this mean she's trying to shed?

I keep her in a 20 gallon tank that is between 80-87 degrees and between 50-70% humidity most of the day. The tank dries out while I sleep. I'll wake up and the humidity will be about 20% but I'll immediately dampen the towels and put them back on top of the tank. Without the towels, the humidity is at 10%. She has a hide and a water dish that is constantly kept full and is rinsed regularly to prevent bacteria growth.

Can anyone tell me what I'm doing wrong or if I'm over reacting?