HeArT BeaT

Hey, did you all experience this? When you miss some particular person then you wish to see them. But when they are in front of you, you will scare, heart beat will be abnormal and don't dare to look at them face to face at all. When they talk to you, you don't dare to talk much and will reply it with eyes looked at the floor or other place. What is that means? I never experienced this before. I had ask my friend and even my sir about it. They all said that I really like that person. Oh no, is that real? I really not sure about it. Anybody can tell me?