Jennifer Lopez is a workaholic.

The 'On The Floor' star - who has five-year-old twins Max and Emme with ex-husband Marc Anthony - is always working on new projects and ideas and though her work ethic is admirable, it makes some people around her uncomfortable.

A source said: ''Jennifer is constantly working, 24 hours a day. She makes phone calls at all hours of the night. She'll have an idea and work non-stop until it happens. That kind of work ethic is why she's had success, but it's hard for people to deal with.''

The source adds that the 44-year-old singer - who has returned as a judge on 'American Idol' this year - is worried if she has a break she will lose her status and profile.

The insider added to America's OK! magazine: ''She's afraid that if she takes time off it will all be over. She actually took a break when she was with Marc Anthony and had the kids. Her career kind of stalled. She freaked out. She got everything back up and running because she was afraid. She feels that if she's not on top of everything it will go away.''