In the groove with pop and pregnancy

Sadie Frost, 46, is curled up on a sofa while rehearsing her new one-woman show, Touched... Like a Virgin. She looks a bit confused by the script and feels like hiding behind her hoodie: "You're so exposed doing a solo show," she says.

Not only does she play a Bridget Jones-style character called Lesley, who at 38 wants a baby – but also the entire cast of all Lesley's family and friends. Intriguingly, her character is obsessed with Kate Moss, who is Frost's real-life best friend.

"Kate's been helping me run through my lines a lot and wanted me to practise all the parts she is mentioned in," says Frost: "Kate has one of the best senses of humour – she has helped support me in preparation for this role and will be coming to the show along with the rest of my friends and family."

It's no wonder that Frost feels as if she is spinning plates. "When Lesley is giving birth, in between puffing and panting, I also switch to playing the doctors and nurses," she says.

This is the sequel to Touched for the Very First Time in 2009, when Frost played Madonna-obsessive Lesley from a 14-year-old virgin, in her West End debut.

The play was not written for Frost, so playwright Zoe Lewis made the decision to include Moss as an iconic figure before Frost was offered the role. "It was a complete coincidence," says Frost. "Lesley moves her obsession from Madonna to Kate Moss because she sees her as a modern woman who is doing it right – she has a career, a family and still has a social life, but doesn't feel the need to have a TV show about that social life."

Frost had one child with Gary Kemp and three children with Jude Law, but still identifies with Lesley, who wants a child in her late thirties. "It never crossed my mind after my divorce to start a new family or to find a new relationship. I was so busy working. If I could go back in time, I'd have thought exactly how Lesley does. I'd probably have gone to a sperm-donor clinic in Sweden and got inseminated."

Frost is taking a more relaxed attitude to the play than she did in 2009 when she dedicated herself "in a Zen-like way" to the role with no distractions. "I don't have a nanny at the moment and I have to do the school run," she says.

This time, playwright Lewis has blended "the old and the new material" to create a musical, with pianist and cabaret singer, set in the intimate space of the Soho Theatre.

Having starred in various films including Francis Ford Coppola's Dracula in 1992 and Shopping with ex-husband Law in 1994, theatre is a relatively new experience for Frost.

She put acting on hold to have children and became a dab hand at new careers. In 1999, she started up fashion label FrostFrench, which has two lines sold in Debenhams – FrostFrench and Floozie. "We are expanding to handbags and bath and body gifts now." She has also just designed kitchens for a development in Docklands.

"This play", Frost concludes, "is about having fun. It is perfect for groups of girls coming for their office party – and there are saucy and sexy bits for the men."

'Touched... Like a Virgin', Soho Theatre, London W1 (020 7478 0100; sohotheatre.com) tomorrow to 9 June