Here is a fact for you to consider. Weight loss and dehydration can decrease your performance by 30%. Laxative use can result in dehydration and long-term detrimental to your intestines. Since your goal is doing well in track this year, laxative use will not help you reach your goal.
Currently, your weight is proportionate to your height. Actually, you could weigh up to 117 pounds and still be an appropriate weight for height. Why not focus on increasing your muscle mass, which will carry you much better over the track hurdles? After all, at 95 pounds, you would have 3 fewer pounds of muscles to compete. Take a look at some female Olympic track stars. They have large, muscular legs for competing. Why lose weight? You should be focusing on gaining muscle, even if you stayed around 100 pounds. For this, you need to work with an athletic trainer or exercise physiologist.
I would suggest you talk to a school counselor or better yet a psychologist with experience in eating disorders about your obsessions with body weight and perfectionism. These are symptoms of other issues that you need to deal with. Deal with this now or it could get out of control. You already have some of the symptoms of anorexia.