Kaley Cuoco is paranoid and worried about her struggling marriage to Ryan Sweeting

Actress Kaley Cuoco is reportedly "secretly worried" about her marriage to tennis player Ryan Sweeting.

"The Big Bang Theory" star has been denying rumours that her relationship with Sweeting is on the rocks, but it is reported that she has her own doubts.

"Kaley is really paranoid...she doesn't let him out of her sight. She always asks Ryan who he's with and never knows what he's doing. She'd flip if he didn't answer his phone. And it drives him crazy,” US' OK! magazine quoted a source as saying.

“She is secretly worried she doesn't know him that well," the source added.

The pair got married on New Year's Eve in 2013 and were engaged after only about three months of dating.