Adam Margolis told a woman he met through an online chatroom he wanted to marry her just hours before killing her.
The 41-year-old has been charged with murdering Mai Yia Vang, 26, in Bendigo in February 2018.
Police found her body lying on a mattress after Margolis sent a 12-page email to a group of former acquaintances outlining he had killed a woman and planned to take his own life.
Margolis told police after his arrest that Ms Vang, who he met via an online chatroom called Omegle, had "goaded" him into attacking her by triggering "flashbacks" involving childhood abuse allegedly inflicted by his stepfather.
The former IT developer on Friday said while he loved Ms Vang she had repeatedly "run into" him and made remarks about this abuse on the night she was killed.
"I felt the most amount of love for a human I've ever felt in my life," Margolis told the Victorian Supreme Court.
"I said I would marry her if she could control these reactions ... and (later) 'I'm worried I may attack you if you keep saying this'.
"I told her that was the one thing that would be extremely triggering for me."
The accused man said he had a 15-minute "flashback" that involved recollections of fighting his stepfather before "waking up" on top of Ms Vang's lifeless body.
"I was shocked and felt sadness, confusion and distress," Margolis said.
Ms Vang met Margolis online in January 2018 and agreed to move in with him in Bendigo the following month.
The court previously heard Margolis became angered after discovering Ms Vang remained in contact with an ex-boyfriend, who has testified that she was a quiet, reserved and intelligent person with a good sense of humour.
When police asked the Bendigo man if he took Ms Vang's life, Margolis said that wasn't an "appropriate way of phrasing it".
"I'm not the person you're obviously trying to make me out to be," he told police.
"She drew me into a flashback intentionally, knowing full well what would happen."
His barrister, Bruce Walmsley QC, has said the trial hinged on whether the jury could find that Margolis intentionally killed Ms Vang.
The trial continues on Monday.
Australian Associated Press