If I was you, I would consider all my options.

The correct choice is "was" because the phrase should use "were" in a subjunctive mood, which expresses hypothetical situations or wishes. In this context, "If I were you" is the appropriate phrasing, as it reflects an unreal or contrary-to-fact situation. The subjunctive mood emphasizes that the speaker is not actually in the position of the person being addressed. Therefore, changing "was" to "were" would correct the grammar error in the sentence.

Each of the other words—consider, all, and options—are correctly used in the sentence and do not require modification. "Consider" is the appropriate verb for reflecting on choices, "all" correctly modifies the noun "options," and "options" is used accurately to imply the various choices available.