"To be honest, I was very inactive on it in the last year.
"To delete my Instagram - I had to email my publicist to get the password. Twitter I used to have a bit of fun with back in the day but I think I've tweeted twice in the last year."
On the reality of living life out loud on social media, he said: "The more public interest in you, the more horrible people become. People start to say disgusting things about your family, about your children. What's the point?"
Dornan was tight-lipped about season three of hit BBC series The Fall, which is set in Belfast and has him playing Paul Spector, a bereavement counsellor, married man and unassuming father of two by day and stalker and killer of women by night.
But he said: "You can expect the unexpected. There's quite remarkable turns in the third season that I really genuinely think people won't see coming that are hugely exciting."
The series co-stars Gillian Anderson as Stella Gibson, the London detective sent to crack the case.
"You know, that job changed my life," Dornan said of the series. "They're like family to me and I'm forever grateful for it to be a part of my life and, you know, I would play that character to my dying days if I had the opportunity."
Does that include a fourth season?
"I don't know anything about that," he smiled.
On the Fifty Shades front, which includes back-to-back filming of the steamy trilogy's last two instalments, Dornan is enjoying the prospect of life post-Christian Grey.
"It's satisfying to put an end to any job I think, and to do two back to back, I think there's an element of relief that the work is done and you're happy with it," he said.
He said his wife Amelia Warner spent some time on the Fifty Shades sets.
"Yeah, a couple of times on choice days," he said. "There were some days where it probably doesn't make a lot of sense for her to be hanging around."
The franchise's second movie, Fifty Shades Darker, is due out in February. The third, Fifty Shades Freed, is scheduled for February 2018.