6 months with no weight loss

So I was 170 pounds and 5'5 when I decided I really needed to take my diet seriously. I am now averaging about 145 pounds. As I am aware, this is not terribly heavy, especially for my height and frame, but I still have a stomach bulge and flab that is pretty unnecessary. Unfortuanatly, through a combination of increased body confidence and a more independant life-style, I feel like I have fallen off the rails...or have I? When I think back on the past 6 months of following my diet, I realise that very little has changed. In fact, since coming home from school, I have been eating better than ever! Other than a few low-calorie tea biscuits with my coffee, I eat mostly balanced meals with grains and veggies. Since I'm only 21, and I really only gained all my weight in my late teens, am I just obsessing over the relatively little weight I must loose? Currently, my goal is 125 pounds. That seems reasonable, but as I've heard people say, the last 15-20 are very difficult to drop. I don't plan on giving up on my diet, thyroid problems mean my metabolism is already slow, but considering how comparably easy it was to drop the first ten pounds, this is really discouraging! Anybody else know about these sort of weight plateaus? I understand that my problems may seem small to someone who has to loose 100+ pounds, but just think of a 6 month plateau! I can't be the only one!