My ball python has been eating regularly, but still appears underweight?

[nightrainfalls]

I've had her for about two months, and she wouldn't eat for the first two and a half weeks, but since then she's been eating a large mouse every five days like clockwork. Humidity is good, but temps have been slightly off-I live in Minnesota where it tends to be freezing during this time of the year and my heat has been wonky. A guy's coming out to fix it on Monday. I have an UTH and a lamp, but the ambient temp's been in the higher seventies rather than the 82-84 range that I like.

Undernourished BP's have a very distinctive look. The spine starts to show, and the body gets a steepled look to it. If you can't see how undernourished the snake is in a photo, then it is probably not undernourished.

Is your snake's dorsum well rounded?
Can you see the spine?
Is it just loose skin that is worrying you?
Is the snake's belly pink at all?
Are the snake's eyes cloudy at all?
Are the snake's colors dull?
Does the snake have a clean fresh water source?
Does your snake have a high humidity hide?

David