expression, godan verb (-mu)
worry oneself sick; agonize over
Emphatic expression meaning to worry intensely and at length, often to the point of distress. The repetition of 悩む reinforces the depth of the worry.
将来のことで悩みに悩んで、夜も眠れなかった。
I worried myself sick about the future and couldn't sleep at night.
彼は進路について
After agonizing over his career path, he decided to study abroad.