We don't know. Marriages have been mentioned in "Blink" and "The End of Time", and the Doctor married River Song in "The Wedding of River Song" (the fact they're married was confirmed in the later "The Angels Take Manhattan"). The Doctor also apparently had a Las Vegas wedding to Marilyn Monroe in "A Christmas Carol" but he doesn't count that as official. Also once with the 1st Doctor in a episode with Aztecs he accidently was engaged to an old woman.
And he might have had a relationship with a women to have a child, then to have a grandchild (Susan) so he might have been married then.
Finally, the Doctor was married to Queen Elizabeth the First as seen in "The Day of the Doctor".