Well the daily recomended caloric intake is about 1900 for female women who are lightly active which is walking about 1 mile a day. It is not recomended to cut your calories more than 500 below the recomended allotment so if you add the 500 calories saved a day times 7 that is 3500 calories lost in a week which equals one pound of body fat. So thats just to help see how much your caloric intake affects your weight.
It is important to be happy with your weight but also know that what you think is an appropriate weight may in fact be unhealthy. Here is a link to a body mass index calculator. It is easy to use and may help. Though not all people are the same if the index is saying you are drastically underweight it may be correct.
Calculate your BMI - Standard BMI Calculator