Katherine Heigl has never been tempted to cheat on husband Josh Kelley - she is just so good! But she says that he better not cheat on her either!

The ‘One for the Money’ actress says she could never have sex with another man because she needs to have an “emotional” connection.

Writing on her iVillage blog, Katherine – who has a three-year-old daughter, Naleigh, with Josh – said: “I have no desire to physically hook up with any man other than my husband and have been a serial monogamist from the moment of my first serious relationship at 20. I have never been able to connect with a man sexually without it becoming emotional, without giving a piece of my heart and soul to that connection.

“I understand that every human being on earth wonders if the grass might be greener in other pastures, but I could never imagine myself really going there or really wanting to. I guess the relationship I’m in is so consuming that the idea of a dalliance with another man sounds exhausting. It’s hard enough to make one connection work. I can’t imagine, even for four days, splitting myself between two!”

However, Katherine, 33, admits things aren’t always perfect between her and musician Josh.

She said: “We’ve had some pretty explosive fights over the years trying to make our marriage work, but it’s been worth it. I do not want to live my life without Josh in it and will do everything I can to make sure I don’t have to – except give him the freedom to don a costume and mask and bang some other chick.”