Young said Edwards stopped returning his calls in January 2008, as Edwards was suspending his White House bid. Young and his wife, Cheri, had been asked to keep Edwards' mistress, Rielle Hunter, out of the media spotlight.
But when months passed with no call from Edwards, Young said he and his wife grew tired of sharing a house with the increasingly-demanding mistress, and he demanded a face-to-face meeting with the senator.
The two men met in a hotel room near Washington on June 18, 2008, when Young said he was asked to keep the secret for longer. The tension during the meeting grew so tense that the men were yelling at each other and were close to throwing punches, Young testified.
Young is a key prosecution witness against Edwards, who is accused of conspiring to use secret payments from two wealthy donors to hide Hunter during his White House run. Edwards has pleaded not guilty to six counts related to campaign finance violations.
"He said he loved me and that he knew that I knew he would never abandon me," Young testified.
If convicted on all six counts, Edwards faces a maximum penalty of 30 years in prison and as much as $1.5 million in fines.
During cross-examination, Edwards attorney Abbe Lowell peppered the former aide with questions about subtle inconsistences between Young's testimony and accounts of his story in grand jury testimony, media accounts and his book. One juror appeared to fall asleep during the third hour of cross-examination.
Lowell asked Young if he had once tried to be like Edwards, going to the same dentist, hiring his boss' former homebuilder to construct his dream house. He asked whether Young had fallen in love with Edwards.
"A lot of people in the country did," Young replied.
"Did you fall out of love with him?" Lowell asked.
"I did, yes sir," Young replied.
"You really hate him, don't you?" asked the lawyer.
"I have mixed feelings," the former aide said flatly, looking straight ahead.
The Associated Press contributed to this report.