The important thing is to be healthy, not to consider the number on the scale. I was very skinny when I was younger because of a fast metabolism but I was not strong or healthy because I didn't exercise.
How tall are you? Depending on your height 118 pounds is perfectly healthy. 99 pounds is underweight.
I would say eat healthy and exercise. With exercise it is good to not do the same type of exercise everyday (ie do push ups one day for strength, running another day for cardio, etc) Whether or not you lose weight is not so important; you can lose fat but gain muscle so your weight evens out. So you might weigh the same but it will be a healthier weight. Also you need to be sure to eat more if you exercise so that you aren't starving yourself.