My body is backwards when it comes to caloric intake. Help?

You don't mention your age or gender, so it's hard to say. 1200 to 1400 calories is probably way to low; depending on age and gender you may need almost twice that a day just to run metabolism. Burning 800 calories in exercise on top of a restricted calorie diet---yes, your body is in starvation mode. Your nutritionist is right. You're not understanding that your body is not going to get smaller when it thinks you are starving. What little calories you take in will be stored as fat and your body won't make something as metabolically active and calorie-demanding as muscle. You're very careful about your calories in, and that's great. But you need to re-ess what that number should be, and come a lot closer. When you burn that many calories in exercise, you can eat slightly more than your basal metabolic rate demands, you'll still burn off fat, still get smaller.