Plus if you have just started the gym, you will initially retain water in your muscles which often shows as a gain BUT this is only temporary and will even itself out in a couple of weeks. I started a new workout regime with lots of lunges last week and lost 1/2lb. I'm not worried, I've lost an inch off my hips in 2 weeks! Get your tape measure out and put all your measurements down, the weeks when you don't lose weight you can check you're losing inches. DONT be ruled by the scales!
I'm the same hun, i stuck to plan 110% last week, did more exercise then normal - auqaerobics, swimming two times, and hiking up a mountain and i only lost 1lb - was well gutted - but i retained water due to the amount i was doing, it will come off, i bet you will get a fab loss next week xx
Don't get down hearted about it, if you know you have stuck to plan then the scales will reward you, sometimes it just takes a week for them to catch up when you change something and if you retain water a bit when starting excersise, this is probably why. Don't let it wobble you.
Maybe try doing your measurements too as often you don't lose weight on the scales but you will lose inches. Alot of people in my class who do a lot of exercise have noticed a huge difference to their shape.