Final answer:
The correct phrase is 'me dormí', which means 'I fell asleep' in Spanish.
Step-by-step explanation:
The correct phrase is me dormí, which means 'I fell asleep'. The verb 'dormir' in this context is reflexive, so you need to use the reflexive pronoun 'me' before the verb. The past tense form of 'dormir' is 'dormí' with an accent on the í. Therefore, the correct phrase would be 'Cuando yo volví a casa, me dormí enseguida'.
Learn more about Spanish verb conjugation