The singer opened up on KIIS FM's Kyle and Jackie O radio show about his relationship, telling the radio hosts that he and Jules broke up because he was just a "kid".
"She left me before," he revealed. "She left me because I was a rubbish boyfriend..."
The 33-year-old continued, "I was not a gentleman. I didn't believe in opening doors.
"It took her breaking up with me for me to realise I was a bit of a douche".
Guy, who just released his new single 'Bloodstone', also said that he is the 'talker' of the relationship and is the one who has to resolve any fighting.
"I just want to make sure she still loves me."
Jules and Guy began dating as teenagers and tied the knot in 2008.
The couple are parents to sons Hudson and Archer.