There are numerous synonyms for the phrase "worry about". To be concerned or fret about can be used to convey the same meaning. Other options include feeling anxious, troubled or preoccupied. Some people may say they are bothered, disturbed or perturbed by something. To express nervousness or unease, one might say they are apprehensive or fearful. Those who are consumed by a sense of impending doom might say they are plagued by something. For those who are uneasy or in a state of agitation, the word agitated might be appropriate. However you choose to convey it, the sense of worry about something can be overwhelming, and finding the right phrase to describe it is essential.