Baby rolled at 3 weeks

So we’ve been swaddling our 3 week old and she’s been sleeping like a dream. Two nights ago she woke up once for a feeding and around 7 am I heard her grunting like she was waking up again to eat. I rolled over in bed to pick her up and she was FACE DOWN. I freaked out and now don’t know what to do for her sleep wise. My husband put her bassinet mattress in slanted and I think I probably laid her down sideways after her feeding so I think those were two factors but now I’m terrified. Last night we swaddled with both arms out and she slept awful. Any suggestions?