The Take That star ended his main five-year affair with mistress Neva Hanley, 24, in September 2009, just weeks before his wedding in October.
Mark says the other flings were one-night stands that took place when he was on tour with the band.
'I don't know how many girls there were in all,' he says. 'Maybe 10.'
Bandmates Gary Barlow, Howard Donald and Jason Orange didn't know about the affairs.
Mark, 38, who started dating Emma five years ago, saw their wedding as a fresh start.
But despite ending his affair with Neva, the pair remained friends and he even sent her a series of cheques totalling £12,000.
Last month they agreed they can no longer stay in contact for the sake of his marriage.
'She phoned me the week before I got married,' he tells The Sun.
'She said she had lost her job and was going to lose her flat - and asked if I could help her out...
'I wasn't paying Neva with the intention of keeping her quiet.
'I'd have no money left if I was paying them all off...'
Mark and Emma are parents to Elwood, 3, and Willow Rose, 1.
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