How many calories should I be eating?

If I burn ~600 calories when I work out how many calories should I be eating to lose weight? I'm 5'4, female, 20, and 135 right now (but I fluctuate a lot between 135-140). I work out at least 5 days a week and right now I eat between 1200-1400 but I'm not losing weight like I should be. Maybe I'm eating the wrong food? If anyone has help/advice it would be appreciated. Thanks!