I would call on Archangel Michael, Uriel, Gabriel, Raphael and the Mighty warriors of light on earth, and ask them to remove all dark and negative energy from around you. If this E.T. won't leave you then it's likely not your guide. Positive spirits will respectfully leave when asked to do so. Every time I've asked a negative entity or E.T. to leave they won't or I even get a "No!" or "I'm not leaving" The positive entities will back off as soon as you ask them to though. I also have the name of a book you could read that talks a bit about greys and other aliens in a few chapters let me know if you would like the name.