The singer, 30, was brought on to the BBC show as a new judge, replacing Arlene Phillips, 66, which prompted a huge media backlash.
She told Fearne Cotton on ITV2's Fearne And... Alesha Dixon: "It really upset me actually because I felt like my character had been criticised in the papers and that was really tough and I was just sitting there thinking 'is it really worth it?' and 'do I really want this?'"
She continued: "But with each negative thing I was reading it was actually firing me up to want to do it even more.
"This is just the way of the industry, I'm the guinea pig in the middle of a media hoo-ha, you put things into perspective."
Alesha also described how she felt when she was dropped from her last record deal, saying: "I went into a mini-depression because I wasn't fulfilling me."
:: Fearne And... Alesha Dixon is on ITV2 on Thursday November 5 at 10pm.