Strange Problem - Looking For Medical Answer

Hi, i am a 23 year old male. I have a weird problem. Whenever i feel dangered, or threatened or if i see something which i feel hurt or angry, i get a sudden pain on the top back side of my head, which then shoots down to my limbs like a shock wave. the pain is similar to someone cutting off the top of my head (though now its not so prominent as i'm used to it). During this time and for a short time period after this happens, my entire body feels super strong and fast and i feel very confident physically and mentally. i can assure this happens as i have tested my response after this happens. When i was young i could invoke this just by concentrating hard enough, but since the pain was too much and as it was scary, i stopped doing that for a long time (around 14 years) and now i can only invoke it to a small extend now. but the reflexive ones remain the same. in order to check if this was a natural phenomenon, i had asked some of my close friends regarding this. all of them denied having such an experience. Is there a medical explanation for this problem? Kindly help. thanks...