Same happened to me a while back (well, 10 years...lol). I went on a healthy eating plan, and did lots of exercise. I was 11 st for 5'9 (which now I realise wasn't that overweight!). In two months, I lost a whooping....4kgs (about 8lbs)....lol
I was very disappointed to say the least. But then I went back home and tried my clothes on!!!! Nothing fit anymore, and I'd gone down 2 dress sizes! :O)
So, instead of measuring weight loss, it's better to measure inches lost. Since you exercise, you build up muscle, which weighs comparatively more than fat. Plus, you'll definitely see results, when maybe you won't so much with your weight.
Keep at it, you're in the right path and you will succeed!