Mila Kunis felt she had been ''punched in the gut'' when she realised her feelings for Ashton Kutcher.

The 34-year-old actress is now married to her 'That 70's Show' co-star - with whom she has three-year-old daughter Wyatt and 19-month-old son Dimitri - but has admitted that their relationship started as just a ''hook up'', until Ashton told her about another woman he had been seeing.

She said: ''I did a movie called 'Friends With Benefits'. He did a movie that was very similar called 'No Strings Attached'. We lived our movies out. We were just like, let's just hook up. Let's have fun. We're both single. We both trust each other. Everything's great.''

The 'Bad Moms' star admitted she attempted to call things off with Ashton after realising she had feelings for him, but he showed up to her home the following day and asked her to move in with him.

She added: ''I felt like I got punched in the gut, literally overnight. I was like, you know what, I actually care about you. I don't want to mess anything up so I'm just going to walk away before it becomes too much. And he was like, 'Got it.' And the next day, he showed up to my house and he was like, 'Move in with me' and I said, 'OK.'''

Mila also recalled the first time she had realised Ashton, 40, was attractive, at an awards show several years after having worked with him on 'That 70's Show', where he had been her first kiss when she was just 14.

Speaking during an appearance on the 'WTF with Marc Maron' podcast, she said: ''I was looking around, and there was a really beautiful man from the back. I was literally like, 'Oh, he's kinda hot.' ... And then he turned around, and I was like, 'Oh, my God, it's Kutch.' I thought it was the weirdest thing that I was checking this guy out, and it was someone that I had known forever.''