1
general::
Phrase(s): worried sick (about someone or something)
very worried or anxious about someone or something. • Oh, thank heavens you are all right. We were worried sick about you!
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, worried to death. Extremely anxious, as in Her parents were worried sick when she didn't come home all night, or We've been worried to death about the drop in the stock market. These somewhat hyperbolic phrases (one could conceivably feel ill from worrying but would hardly die from it) date from the second half of the 1800s.
American Heritage Idioms