Jennifer Aniston is reportedly feeling "insecure" in her relationship.

The actress is dating Justin Theroux, who she worked with on the movie Wanderlust. The pair have been beset by rumours they are planning to marry and have children, although they aren't engaged yet.

It's been claimed Jennifer feels ready to the tie the knot and is getting worried that time is running out for her.

"Jen is, unfortunately, feeling quite insecure in the relationship at the moment, so the next few weeks are crucial. She seems so nervous she can hardly breathe," a source told the British edition of Grazia.

The couple recently travelled to Paris for what was said to be a make-or-break holiday. They seemed relaxed and happy on the trip and so it is thought it helped them grow close again.

"The plan for Paris was to focus on romance and one-on-one time away from LA," the insider said. "They are both really hopeful things will get back on track."