The singer-and-songwriter dated the blonde beauty for nine months between 2006 and 2007 and in 2010 gave an interview describing what Jessica was like in bed.
However, he now says he regrets the comments but he admits he did it to make himself look more exciting.
The 34-year-old star - who has previously dated Jennifer Aniston and Cameron Diaz - told TV show 'All Things Considered': ''I had nothing to say. I was going through a time in my life where I didn't really want to share what was going on, but I didn't want to be boring.''
''When you're just open, but not honest, then you start free-associating garbage. It doesn't mean I can go back and scrub it out, but I understand it now.''
During the interview for Playboy magazine, John said of Jessica: ''Yeah, that girl is like crack cocaine to me. Sexually it was crazy. That's all I'll say. It was like napalm, sexual napalm.''
She added: ''I don't want people to know how I am in bed!''