EXCLUSIVE From X Factor to Hollywood, Katie Waissel has bagged herself an A-list boyfriend - Leonard from The Big Bang Theory

X Factor star Katie Waissel is secretly dating Johnny Galecki, who plays geek physicist Leonard Hofstadter on The Big Bang Theory, Now can reveal.

The couple have been on a few dates and things could be hotting up.

Our Hollywood source tells Now: ‘They have been seeing each other for a few weeks now and it’s going really well. Johnny is really private and Katie isn’t one to splash her love life around so they have been keeping a low profile.’

The couple were first spotted on a date at Chateau Marmont two weeks ago when Johnny, 39, was seen sneaking into the back of Katie’s car and hiding on the back seat as she left the celeb haunt. Katie, 28, even posted a link to the video on her Twitter but hasn’t spoken publicly about the fledgling relationship.

Katie, who was on X Factor in 2010 and is now living in Los Angeles working with her band, Red Velvet, has hinted that the relationship is going well, tweeting, ‘#sohappyrightnow #thisislife‘.

Johnny and Katie are both down to earth and spend most of their time together laughing. It’s early days but could develop into something serious,’ our source says.

Johnny has been single since splitting with his last girlfriend Kelli Garner, 30, in August this year after dating for two years. And Katie has been single since divorcing male model Brad Alphonso after a short marriage in 2012.

At the time Katie told Now: ‘I ended it after two months. I didn’t file for divorce for as long as I could because I wanted to make it work. But the rows were horrific. I remember being on my hands and knees crying, begging him, “let’s just go to New Orleans and forget about everything here.” But he wanted this LA lifestyle. I tried so many different things to make it work.’

The Big Bang Theory started back in 2007 and Johnny secretly dated co-star Kaley Cuoco-Sweetings, who plays Leonard‘s love interest Penny, for two years before they broke up.

‘We’re dear friends, still,’ Johnny has said. ‘Kaley’s not just an ex, she’s a part of my life.’ Kaley married tennis player Ryan Sweetings on New Year’s Eve last year with Johnny and then-girlfriend Kelli attending.

Johnny recently signed a new, three-year deal with The Big Bang Theory that will pay him, along with Kaley and Emmy winner co-star Jim Parsons (who plays Sheldon Cooper) the same $1 million-per-episode salary given to the cast of Friends in its final season.

Katie Waissel and celebrity weddings 2012

Katie Waissel and celebrity splits 2012