quod: Here the conjunction, not the relative pronoun.
Another very heavy line, like line 3. The poem can be paraphrased simply as follows: “Si aliquid peius umquam feci quam quod te reliqui (volens nihil dicere de amore), utinam tu me non ames.” Just as in poem 1, she insists that this love is not to be hidden. What happened the night before? Were there particular people present with whom she did not want to discuss the relationship? (Compare Catullus 83, perhaps?) Or was she simply playing hard to get?