I know that you are probably getting tired of my saying so, but this whole weight thing is a secondary issue. The real issue is that you are associating all of your body issues to a stupid number. I don't look at your picture and see someone who is overweight, I see someone who is trim and pretty.
You don't know what weight you should be at, that is something your body "finds." And when you work out and eat better, your body may actually gain weight. Why? Because you are getting more "fit." I would encourage you to choose some separate goals, body fat %, waist measurement, distance run, weight lifted, etc. Make those goals a "higher" priority than your weight. These other goals can often be things where you can see and measure improvement, even if you weight does not change. This can leave you with a greater satisfaction that your efforts make a difference.
Think about it. Do you want to lose 15 lbs of muscle mass? No. Would you like to lose 15 lbs of fat and gain 15 lbs of muscle? Absolutely. Which will leave you looking better? Is measuring weight a good way of seeing if you look better?