this is after THE prank, you and Sirius had told Snape where to find Remus during the full moon. Remus snapped when he found out, yelling how you and Sirius were dead to him, and to never speak to him again

Regulus said you and Sirius could stay in the slytherin dorms, and share a bed. So right now you and Sirius are in the Marauders dorm packing, when Remus and James walk in..