It appears that Michael Jackson did not have women/girlfriends (in the romantic sense) in his private life or in his public life.
Besides, John Randy Taraborrelli confirmed it:
"No one believed [that] he'd had romances with girls such as Tatum O'Neal or Brooke Shields, no matter how much he insisted he had" (John Randy Taraborrelli, 2009)
Michael Jackson also appeared to be very shy or even frightened of women/girlfriends, as confirmed by Tatum O'Neal who confided in one of her friends:
"How can any girl have a relationship with him? When we're together, he's so shy he hardly says two words … He doesn't seem very interested" (Tatum O'Neal)
Given also his private conversations with his spiritual advisor Rabbi Shmuley Boteach, the singer felt intimidated by women/girlfriends.
Some people even have stated that his public, high-profile dates with some famous women/girlfriends was all an act on his part so as to hide something more sinister.