The 41-year-old No Doubt singer was so unhappy with her body after having second son Zuma in August 2008, she felt too "out of touch" to write any new material ' so the band ended up touring without releasing a new single.
She explained: "I hadn't planned on doing a tour; I'd had Zuma, I felt so gross ' I got so big and felt so out of touch and not cool. I was trying to write this cool record and nothing came out.
"I felt so bad because you've got this whole band waiting, but I couldn't write. So we said, 'Let's go on tour'.
Gwen ' who also has another son Kingston, four, with her husband Gavin Rossdale ' admitted going back on stage was tough because she found performing her old material so emotional.
She said: "We had no new single, we hadn't been on stage together for, like, five years and every night I'd get teary-eyed because of those old songs.
"I'm up on stage and I'm singing songs about relationships I've had and I'm looking over and my kids are watching me. It's very surreal."