It doesn't matter what the scales say, it's whether your jeans are looser! Seriously, I have no idea why people have this issue with what the scales say...
Scales just tell you your mass, but if you have toned up, then your will have become more dense (muscle is denser than fat), so the same volume has more mass. Muscle is always better than fat, it makes you look better, feel better, less prone to injury etc.
Unless you're a man and training to exhaustion by lifting heavy weights you're not going to get massive.
You'll also probably see the scales go back the other way soon as you may well have built muscle and not lost the equivalent fat. It is possible to build muscle in four weeks, particularly at 3/4 times a week.
Also, be aware that a 1 litre of water has a mass of 1 kg, so if you had a big drink before stepping on the scales, that's a big difference in pounds. Also, if you're female, the time of the month and water-retention can make a big difference - some women's weight fluctuates by as much as half a stone a month.
but seriously, ditch the scales! Just concentrate on how you feel, whether your butt looks great in your jeans and whether you can now run for the bus without wanting to pass out. That's the point of going ot the gym, to get healthy and improve your well being.
Good luck with it