be at the end of your tether
From Longman Dictionary of Contemporary Englishbe at the end of your tetherbe at the end of your tetherFED UPto be so worried, tired etc that you feel you can no longer deal with a difficult or upsetting situation → tetherExamples from the Corpusbe at the end of your tether• I had no money, my husband was sick, and I couldn't get a job. I was at the end of my tether.