Is something up with my brain?
 

I can make my brain have this tingle/electrical feeling. I can't describe how i do it but i can make it happen. Is this normal or am i messed up... Sometimes the feeling goes down my spine.It feels really nice but when i do it to many time my brain feels like its going to blow up(Like i over worked on my homework/project) What exactly am i doing? Also, i am 15 and i used to have cancer(retinoblastoma). Resulted in my right eye being removed. Dont know what else to say. Is something up?