R U N was released December 3rd, 2014; when Jah was still broke and no one knew who xxxtentacion really was.
This song describes a guy (probably X) in a ski mask (to hide his identity) raping a girl, as seen in the single verse.
“Run my head” means he’s encouraging the girl to start sucking his dick, which is the chorus of the song. Could also mean that he’s ‘running through his head’ or mind because of the constant negative thoughts Jah’s having because of his depression.