I just wanna know why is this happening to me.

20M, I'm 5'41 (165 cm), I weigh 146,8 pounds (66,6 Kg), I'm Asian, I don't smoke nor drink and I haven't been taking any medicines on a regular basis.

I have been having trouble sleeping lately. I always wake up in the middle of the night. And always after I wake up, my heart starts beating so fast, I don't know who I am or where I am and I don't remember anything. Once my mom came into my room and woke me up accidentally. Even though I saw her face, I didn't recognize her. For some reason I thought she might attack me, so I freaked out. That was the worst one that I have ever had. I haven't told my mom about all of this, because I don't want to worry her.

I thought that I might have just been watching too many scary movies. But I've been also thinking about the fact that my head was hit once about 3 years ago as a possible reason for all of that. I was in school and playing with two other boys at that time.They lifted me up and dropped me accidentally. As a result, my head got hit on a locker. I blacked out after that. The next thing I remembered was that I was sitting on my chair with my hand covering the back of my head. When I looked around, I couldn't recognize anyone. I was shivering. And when I looked down, there were so many toilet papers with blood on them. I didnt know what's happening, until I realized I was holding one piece of toilet paper in my hand. That evening, my mom took me to the hospital, But the doctor said that there's nothing wrong with my head. They simply took care of my wound and let me go.

Even though that I've been having those "wake up from sleep not remembering anything" for too long already, I didn't pay much attention to it. Until now, it becomes so serious.