I think it's just a sad truth that many people encounter when they change their lifestyle - weight is not easy to lose if you do it sensibly, ie through healthy eating an exercise, and as I'd mentioned in another very similar thread, there can be a million and one reasons why this isn't happening. So again: be very honest with yourself as to how much you're actually eat and how hard you are actually pushing yourself when you exercise.
Just remembered another thing - I think that by the time we hit our late teens we have a like a basal number of fat cells that we'll always have, so what happens when you lose weight inititally is that these are emptied to a certain degree - once you get down to your like basal level or whatever it is then harder to get rid of completely which is why people sometimes plateu and then the weight starts falling again - also your body will take time to adapt. I know I used to have the worlds slowest metabolism, still have a fairly slow metabolism, but over a couple of years it's changed, so I seem to be losing weight quite quickly.
Sorry end of essay... again... but honestly, just keep at it, so long as you're not eating a lot more because of the extra exercise, then it WILL happen, so stay positive
