Billie, who is married to actor Laurence Fox, says marriage is often filled with 'stupid' arguments.
Piper, 28, told British Psychologies magazine: 'I don't ever feel completely even keeled when it comes to love and marriage and companionship.
'That's a lot to do with my personality. I feel like it is not still.'
The Secret Diary Of A Call Girl star added: 'Being in love isn't something that goes, 'Oh, this is it then'. It's more dramatic. It can make you feel sick and then out of control and hyper.'
Talking about the arguments which can occur she said: 'They're usually something really stupid, often born out of being exhausted. It's that endless fight of trying to feel settled and trying to keep a certain level of cool.'