"worried endlessly" is correct and can be used in written English.
It is used to describe someone who is continually anxious about something, often to an excessive degree. For example, "I worried endlessly about my upcoming test."
She worried endlessly; she woke at four to jumbled, urgent thoughts and couldn't get back to sleep.
He adored and cossetted her, worried endlessly over her, encouraged her, and, under the influence of frequent black moods and alcohol, sometimes fought viciously with her.
She worried endlessly about one of Joel-Peter Witkin's pictures: "What am I going to do with that breast on a plate?" But then she recalled an anecdote.
My colleagues and I worried endlessly over our positions in the hierarchy and had worked out to several decimal places which assignments were to be coveted, based not on their intrinsic merits but on their status.
Critics have compared London's Olympic logo to a bad drawing of male genitals, said that the mascot looked like an insane alien, groused about the ticket-allocation process and worried endlessly that once the Games come, Londoners will be sucked into a transportation-and-security nightmare.
Meanwhile, my dear friend and Weekly Standard Editor Bill Kristol, who worried endlessly about how ObamaCare would turn America into a high-tax, big welfare-state country, is resolutely blasé about the intrusive scope of the Arizona law because supposedly it just won't apply to too many people.
The Fullers knew they would worry endlessly about its structural integrity.
The contestants were shown worrying endlessly in a holding room, then taking a long walk to face the judges.
In fact he was deeply caring and nurturing, worrying endlessly about the lives and progress of his colleagues.
As a parent, Bovell says she worries endlessly about the opportunities that will be available to her son once he leaves school.
But I can't focus on those things as positives because as great as they are for him now, I worry endlessly about what the future holds.
