A body fat percentage of 18 (%) is amazingly/athletically low. I encourage you to eat more calories, especially carbohydrates and work on adding muscle to your lean physique. You won't appear nor have much "flab." A calorie deficit below 1200 is considered a "starvation level" calorie intake. Since your calories are not meeting with your energy needs, it is preventing you from filling out with more muscle and body weight. At 5'4" your predicted weight is closer to 120 pounds. Best to you!