I'm going to be a bit controversial... I personally think that BMI is a load of rubbish.
I believe it was actually devised to analyse groups of people, not just individuals and it just doesn't make sense. Some people are clearly healthy i.e. atheletes and professional sports men and women but might be considered Overweight because of their muscle mass. It's silly.
I'm the opposite- I am 3lbs off being a 'Healthy' BMI. Load of crap. I have PCOS so 90% of my weight in on my stomach. I can see it there and I know that much fat is not healthy. BUT, my Doctor believes in it and if/when I try to have kids, if I have any problems I know they'll be much more willing to help if I am a 'Healthy BMI' (In case I have PCOS related difficulties). But I probably know that a good 20lbs will have to be lost before I am 'healthy'.
Just my 2p on the matter. I personally think the best way to measure is your body fat%. I'll be asking Santa for some snazzy scales this Christmas so I can start keeping an eye on that. I want to lose the weight first, then getting the Body Fat % right will be the next aim