this question does not ask to identify the bad things that happen to Gregor that cause his crisis. Instead, the question asks you to focus only on how Gregor's thinking causes his crisis.
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first............ he thinks about his job. He hates his job, he hates going there, and he hates being the only one in the family who steps up to take care of the family (his family has also come to expect this).
second, thinking about money or lack thereof shames him, which leads to further isolation
third, he thinks about the isolation others have imposed on him and the feeling of being unloved. This comes to a aprticular head when Grete begins to ignore him and stops taking care of him.