What Causes Rapid Heart Rate On Exposure To Sudden Noises?

I am 25 year old girl. My problem is that i get scared of noises. My heart beat gets fastern up and my breath automatically get faster i cannot breath properly it makes me feel like i am dying. I cannot take proper sleep as lots of little noises makes me awake even i get up from my sleep bcz of air voice. I get very scared of natural disturbance like lightning, Storm and heavy rainfall sometimes i started crying. Since 4 years i am having this problem even sometimes i see structure of human body though i do not believe in all these stuff but it makes me very scared. Please suggest me something and tell me why this is happening with me.