The 40-year-old actor has played Mandy Richardson in the Channel 4 soap on-and-off since 1996 and said it was her connection to Hollyoaks that started her down the route of swimwear and lingerie shoots.
Dunn told Sky News: "The reason that I've done so many shoots like this, lads mags and things, is because of my connection with the show. That is why I was shocked and disappointed that they weren't able to support me in my decision to just move my content to another platform."
Dunn has left the soap after failing to reach an agreement with bosses over her use of the adult only subscription site.
Hollyoaks produced an annual calendar of 'Babes' and 'Hunks' until 2012, featuring its stars in sexy photoshoots.
Dunn said the photos she shares on Only Fans are no different.
She said: "My content isn't explicit content. There's nothing on there that I wouldn't put on my Instagram account - and was doing prior to this."
Dunn went on: "I want to tailor that now to people that want to see fitness, that want to see family, that want to see my relationship, that want to see holiday [photos] and things like that.
"And for the people that did want to see bikini and underwear - the shoots I've been doing all of my life, basically - I've just put it in a different space."
And the soap star feels she cannot back down, as it has become an issue of control over her own body.
She said: "The bigger message in all of this is that I wanted to take control, to take power back, over me, and I was trying to convey that message to other women... then for doing that, I have essentially lost my job... I think it is disappointing that actually for making such a stand, this is the outcome."
A spokesperson for the show told Yahoo: “Hollyoaks is a youth-facing drama with many young viewers, who follow our cast very closely, both in the soap and outside of it.
“We take our responsibility to our young audience very seriously and therefore the show does not allow any Hollyoaks cast members to be active on certain 18+ websites.
“We had hoped we could reach a resolution with Sarah that would allow her to remain in her role as Mandy, but we respect her choice to continue to produce content on OnlyFans.
“In the past four years since her return to the show her legacy character has been an integral part of some our most important storylines and we will be very sad to see her go.”
Watch: The latest soap gossip from Hollyoaks