DENVER — Christopher Watts’ mistress says he lied during their entire relationship, according to a report Thursday in the Denver Post.

Watts has reached a plea agreement with prosecutors in the murders of his wife, Shanann, and the couple’s two daughters.  He will be sentenced in a Weld County courtroom Monday after pleading guilty last week and avoiding the death penalty. Their bodies were concealed on an oil site in Weld County.

Nichol Kessinger told the Post she started dating Watts in July. She thought he was just a soft-spoken man at the end of divorce proceedings.

The report says she found out when his wife and two daughters went missing in August from their home in Frederick that he never started divorce proceedings with his wife. She was 15 weeks pregnant at the time of her murder.

Kessinger said her relationship with him lasted two months.

The report says she called what he did senseless and horrific. It also says she approached investigators before he was arrested and she was involved in several police interviews where she told them details of their relationship and what he said about his missing family.

On Aug. 13, the day that Shanann and the girls went missing, Kessinger told the Post he texted her to say he had been busy and they chatted through the day.

Late in the afternoon, he texted that his family was “gone,” the report says. Watts was arrested Aug. 15 for the murders of his wife and two girls.

FOX31 contacted Kessinger’s attorney, Ed Hopkins in an attempt to get comment from Nichol Kessinger about this story.

“Ms. Kessinger agreed to speak with The Denver Post this morning to help the public learn the truth and prevent misinformation from spreading. She does not wish to comment further at this time,” Hopkins said in an email.