The couple, who started dating in 2009, ended their relationship amicably and there was no third party involved, reported Ace Showbiz.
"Things haven't been ideal in their relationship for some time. There was a lot to work on before they could move forward and get married. Britney had a lot of issues with Jason doing his own thing - in business and seeing his friends," a source said.
"In her perfect world he would have been home with her twenty-four/seven, so that was a point of contention; something they were always working on," it added.
The couple seemed to always put a united front together, but "they've been spending a lot of time apart in the last few months."
Although they grew apart, the source said, "They both seemed happy. Especially Britney, I could tell that she was in a really great place. She smiled a lot. They were both really at ease with the boys."
Spears and Trawick got in engaged in December 2011. They ended their professional relationship to focus on their personal life.
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Trawick was later approved by a judge to become Spears' co-conservator but was subsequently removed after the breakup, restoring her dad Jamie Lynn Spears as her sole conservator.
The couple split just a few weeks after his 41st birthday.
After the split news broke out, Spear said in a statement, "Jason and I have decided to call off our engagement. I'll always adore him and we will remain great friends."
Trawick added, "As this chapter ends for us a new one begins. I love and cherish her and her boys and we will be close forever."