Don't look at the mirror OR the scale!!!
I have a digital camera, but for those who don't, you can get a walmart throwaway for cheap..
Take a photo of yourself now, in a week, take another wearing the same shirt (this is important). In another week, do it again, same shirt. Every two weeks, make a note of your weight, for reference.
After a month, have the photos developed and get printouts, this isn't expensive either. Now, take those photos, and compare them. Do you look fat in picture 4, and bone skinny in picture 2??? what was your recorded weight around the time you look best?
By wearing the same shirt, you are the only different, and you can judge which "you" looks more like "you".
With mirrors, we get tricked, because we change so slowly, our minds see us as us, we can't really pickup on the small differences. In photos, 10 pounds can really show, even on taller frames.
When I was 16, I was told by my doctor that I was 40 pounds over what my BMI should be. So, I cracked down and lost 45 pounds, and I looked like I needed a sandwich! I must stay about 25 pounds over my BMI to look like I won't shatter if I fall. For a taller person, you may need to weigh more over your BMI. The key thing is, try to maintain a weight that looks healthy for you!!!! Just because such and such chart says you need to lose 25 pounds, that doesn't mean you'll look healthy 25 pounds lighter!
I've noticed that people, especially taller men who hang right on what their quoted BMI should be often look like they are physically sickly. As a male who noticed such things, I know that this is going to put him behind the curve on women. What women would want to be with a man who looks overly fat or overly thin, knowing that neither is healthy???