My mother kept thinking about nothing but my coming home.
Literal
Mother [topic-は] I [subject-が] come-home thing [only-ばかり] [object-を] was-thinking
帰宅することばかりを思っていた = 'was thinking only about (my) coming home.' ばかり = 'only/nothing but' — restricts focus to one thing. 帰宅 (きたく) = returning home (formal).