Hang in there Limewave. It is not at all uncommon to hit plateaus during weight loss. I have the exact same problem. It took me almost an entire year to shed 10 pounds last year. I worked and worked and was very diligent about my diet and yet the weight came off very slowly. My body shape changed but the weight didn't.
I think part of it is that you might be adding muscle mass and muscle tissue weighs more than fat. So even though you are doing good things for your body you aren't yet seeing the results as weight loss.
A lot of people restrict their calories too much during dieting and this triggers the "starvation" response in which the body tries to compensate by slowing metabolism. It sounds like you are aware of this phenomenon and aren't restricting your calories too much.
If you can, see if you can get a resting metabolism rate test. My understanding is that this is an easy, non-invasive test and it will give you a sense of what your normal metabolic rate is.
Try focussing on other goals...like working out at least X number of days a week and on continually improving your diet. Try not to put so much emphasis on weight loss as the goal. If you focus on healthy living eventually that weight will come off. If it comes off because you've really changed your eating and exercise habits for the long term it is more likely that the weight will stay off.
-traveller
"It never gets easier, you just go faster." -- Greg LeMond