Ian Paton, 36, of Snowdrop Rise, St Leonards, strangled Kayleigh Hanks, 29, at her flat in London Road, Bexhill. She was found dead there in the early hours of July 21, 2019.
Prosecutors argued Paton killed his care assistant girlfriend after a row developed between the couple about Miss Hanks' friendship with another man.
On Friday (February 7), a jury at Hove Crown Court found Paton guilty of murdering Miss Hanks.
Judge Jeremy Gold sentenced him to a minimum of 17 years in prison - reduced by the 200 days already served in custody since his arrest on July 21, 2019 - before his release is considered by the parole board.
Paton had claimed he applied pressure to Miss Hanks' neck in self-defence after she charged at him with a knife following an argument about a message she found on his phone.
During a two week trial, the court was told Paton had strangled Miss Hanks in front of their seven-month-old daughter.
Shortly after midnight on July 21, Paton called 999, asked for police, and said: "I think I restrained her too hard and she’d stopped breathing."
Giving evidence during his trial, Paton said he was 'sorry to everybody for what they have had to go through' following Miss Hanks' death.
The court heard, on July 20, 2019, the couple had visited Miss Hanks' sister Emma, where they bumped into Miss Hanks' friend Ashley Boxall. Miss Hanks and Paton left together to go home at 6.30pm, the court heard.
Alexandra Healy QC, prosecuting, told the jury that, while at home, an argument developed between Miss Hanks and Paton about her friendship with Mr Boxall, which was 'perhaps precipitated by her having spoken to him that afternoon'.
At 10.50pm, a text from Miss Hanks' phone was sent to Mr Boxall which read: "Have we ever had an affair or can you call me as I knew I would be being accused of it.”
Half an hour later, at 11.19pm, Mr Boxall responded: “An affair, are you kidding me!!!, we’ve known each other for years and there’s never once been even the slightest hint of anything ever happening between us, we’re friends thats it.”
More than an hour later, at 12.34am on July 21, Paton called 999 and asked for the police.
On the call, he said: “Me and my partner have had an argument. We were in separate rooms and she’s...I come back into the other room she’s .... She went for me, she had a knife, I restrained her and she is on the floor now..I think I restrained her too hard and she’d stopped breathing.”
Paton claimed he had suffered cuts to his hands and arms during the fight with Miss Hanks, however, prosecutors said these were fabricated.
Ms Healy claimed Paton cut himself with the knife and placed the knife near Miss Hanks' body.
The court was told that Miss Hanks and Paton had a 'volatile and on-off relationship for about three years', in which they argued regularly.
On one occasion, Miss Hanks told her colleague that she and Paton had been in a parked car arguing when he grabbed hold of the back of her neck and slammed her face into the dashboard of the car, the court heard.
Another time, Miss Hanks told her colleague, Paton had pinned her against the wall by her throat during an argument.
Ms Healy said on one occasion, while in the presence of her sister, Paton demanded Miss Hanks got on her knees and declare her love for him.
Speaking behind a screen during the trial, Emma Hanks said Paton's relationship with her sister was 'ok at the beginning and then toxic'.
Miss Hanks was said to be 'over the moon' when she discovered she was pregnant as an earlier ectopic pregnancy meant she could not have children.
The couple had broken up a few weeks into the pregnancy, the court was told, but shortly after their daughter was born in December 2018, Miss Hanks and Paton got back together.