At the time of standing suddenly i feel pain in a vain at upper left side leg join. After 5/6sec i feel stange feelings. Everything in front of me become darking,head become haevy,feeling lost control on my body and going to faint or die. Immediately i call my mother and sit take water. After 5min i feel better and see whole body is sweating. And i feel cold but the weather is very hot. What was that?why that happen?