4 Month Regression

She used to sleep okay, never great. Now it’s taking a couple of hours to put her down and get her to stay asleep, laying her down over and over again. When she finally does stay asleep, it’s normally for 20 minutes, 40 max. It’s been like this for a week. We’re absolutely exhausted and have no idea what to do. She’ll sleep in our arms okay, but not at all in the crib. It’s feeling hopeless. She’s 4 months old but is a little less than that adjusted (born at 37 weeks), so I’m hesitant to try crying it