The Dancing on Ice contestant topped 13 stone following the birth of her son Bobby in 2010, but has since slimmed down to a size eight.
"I had a career that was based on my body, so people homed in on that," she told the Sunday Mirror. "They were used to seeing me in bikinis, looking great, looking really slim and then I put all this weight on.
"I went for an audition then got a phone call saying I hadn't got the job because I was far too big. I cried and cried. Then I thought, 'Right, I have got to do something about it'."
Even though her weight gain was affecting her career, Ellison put off exercising so that she could spend more time with Bobby.
"I was a pin-up, and there I was with my mum tum. But I was just happy to have my little boy and I didn't care," she said.
"It was hard getting back to the gym as I had been in labour for 92 hours and had to have an emergency caesarean. Then I was breast-feeding and couldn't leave the baby for too long.
"I didn't want to hand Bobby over to a nanny so I could go to the gym. I couldn't have cared less what I looked like. All I cared about was being with him."
Ellison said earlier this month that she wants another child with husband Robbie Tickle.
Dancing on Ice continues tonight (February 26) at 6.50pm.
> Jennifer Ellison: 'I feel guilty leaving family for Dancing on Ice'