The better in shape you get and the closer you get to your weight goal I would advice finding a reputable fitness professional that can accurately test your body fat percentage. For many fitness enthusiasts that get in great shape they will have a phenomenal fat to muscle ratio and because they are in shape their weight may not be extremely low because they carry a higher percentage of muscle.
Lets say we have two females, each are 68 in tall. One weighs 120 lbs and has a body fat of 30% and the other is 125 lbs and has a body fat of 20%. Doing the math we will find that the first has about 36 lbs of fat and lean mass of 84 lbs. The second person although heavier has only 25 lbs of fat and lean mass of 100 lbs. The second person believe it or not will be smaller and fit into smaller clothes because they are more dense and compact and toned and tight.
The example given above is great and BMI is a great tool for those who are overweight and looking to lose weight and be healthier. However once you get in good shape I would encourage you to start to go more toward body fat testing once you are in a healthy range in your BMI.