How can I measure my body fat percentage, w/o going to a doctor?

Answer 1

You can buy scales that measure it....not too much more expensive than the regular scales. (I have one and I bought it at Bed, Bath and Beyond for about 40 bucks) Another possibility is a local health fair.

Answer 2

The pharmacy section of my grocery store has a scale that measures height and weight, and gives you a general BMI with it.
Similar to this: http://www.nhlbisupport.com/bmi/