I had ice cream, and a bowl of cereal with milk before going directly to sleep. while sleeping the food came up my throat choking. why?

Acid reflux?: May just have been too much, too late. On the other hand, the symptoms you describe could represent gerd, gastroesophageal reflux disease. You may have other symptoms which you may have ignored in the past. Belching? Acid taste in throat? Throat clearing? Cough? Should see a doctor.

Full stomach and : Non-upright position can allow food to escape the stomach and cause gag reflex or even aspiration into lungs (cough, choking). You might have poor lower esophageal sphincter tone, hiatal hernia, or gerd. Don't eat right before bedtime, elevate the head of the bed a tiny bit, and if this happens more frequently, see a gastroenterologist. Chronic reflux can lead to esophageal cancer!