Why can I eat 2000-2700 cal/day and not gain?

EatWholeFoods

I eat 2000-2700 daily for many months in a row and no gain. I am 5'1" and my workouts say I burn 300-400 calories 3-4 days a week. I eat a lot but mostly vegetables and fruit and I don't gain weight even if I have cinnamon rolls. Here is the trouble...when I go to lose weight, it takes a month of 700 calorie burns and eating 1200-1400 calories a day all month in order to lose 2 lbs. It seems harder to lose weight and like it takes me longer than other people. Is this normal? I am 120 lbs.