it was like i completely blanked out...

Today i had an argument with my brother, he punched me and the next thing i knew, i was pinning him down and punching punching him (not hard though), the thing is i dont remember getting up or starting to hit him, it was like i completely blanked out, this also happens when things are coming towards me, i was playing rounders and the ball was throw towards me, i didnt react though, i just watched the ball come flying towards me, the next thing i knew the ball had landed and i was just stood there, sometimes when people are talking to me i blank out, either for a few seconds or a little longer, nothing noticable to anybody else but me, but then i cant remember what that person was saying and i have to ask them to repeat themselves, i dont know what goes on at all when this is happening, but sometimes when i blank i eather frezze or im moving but i dont know i am like the incedent with brother. please help. Gx