1500 calories sounds about right, but it depends what you are eating... You must drink about a gallon of water a day, and eat anything with protein in it after a meal because this will speed up your metabolism.
Try eating 5 meals a day also because your body is more efficient when it has less to digest at a single time

Are you doing enough exercise for long enough periods to burn off your calorie intake?
Do you know what your BMI is? There are calculators online which can help you with that, with graphs or points to say where you are and whether you're healthy, overweight, underweight etc..

All I can suggest is eating healthily and regular exercise, maybe it'll just take a while for your metabolism to get up to speed.

In my personal experience I've never been good at gaining or losing weight - I either gained weight from side effects of Depo-provera, or lost it through stress from college and work. My eating has never seemed to effect it luckily, as I eat like a hog at times, but others I go long periods with little food.

Losing weight is simple.
Three rules.

1. Water is the only beverage, add lemon or have tea when you need to switch it up.
2. Burn more calories than you eat.
3. Eat natural food- no more than 3 ingredients per packaged food item. (ex. in a bag of chips under "ingredients:" it should only read salt, potato, and oil. If you can't pronounce something in the food, don't eat it.

Me too facing the same problem