Bergman was charged Monday with recklessly risking another person with HIV infection. He was being held at the St. Charles County Jail in lieu of $250,000 bail.
According to deputies, Michael Brian Bergman, 43, told the woman, "I didn't tell you because I figured you already had it. I don't want to lose you, I love you, and I figured we could be sick together."
Authorities say Bergman, may have exposed at least five men and women to HIV over the past several weeks, and the St. Charles County sheriff's department is looking for more potential victims.
Bergman told deputies he cannot control his sexual compulsive behavior.