My scale will give me varied results 3 or 4 different times. I take the first two matching numbers and use that. Now, if you've done the scale boogy (on, off, on, off, adjust the scale, on, off, etc.) and it still says up 3 pounds, don't stress. A salty dinner, snack or soda last night could attribute to the additional pounds. If its almost TOM or is TOM you may notice some higher than useual numbers. Or it could be the way the moon is aligned with the sun or earth or a particular star's position. J/K of course. Point was it could just be one of those unexplained bodily occurances.
And since you know you've been sticking with the eating/exercising, I agree with Danni. Go out and buy yourself a new scale as a great reward for your self. Then take your old scale and have it meet the hammer or some good ol' concrete!! That'll teach scales to add pounds! Muhahaha!
Again, WTG on the weight loss!