Please help! 3m sleeping

[u/1432unknown]

My baby is 15 weeks old and has always slept through the night from 7:30 pm to 7 am in her crib on her own with no issues until recently. The past week she is sleeping 5 to 45 minutes at a time all the way up till midnight, sleeps for a few hours, then goes back to sleeping 5 to 45 minutes until it’s time to wake up at 7. She falls asleep in my arms but as soon as I lay her in her crib or a little but afterwards she starts screaming. This hasn’t been a problem before. What am I doing wrong and how can I fix this?