10month old won’t sleep 🥴

My daughter is 10 months old, and before last week she slept through the night perfectly fine, but now she’s waking up crying every 2-3 hours so I will hold her. And that’s literally all, I hold her and play with her hair and she falls right back to sleep and I put her back in her crib. I need to figure out a way to help her sleep better because we will have a newborn in exactly 3 weeks and I’m already not getting sleep now, I know I’ll be exhausted with 2 babies waking up that often😩🤣