Almost 6 months and not sleeping like before

My little one will be 6 months next week. He had been sleeping great during the night. Would only wake up 1x for a feeding and go right back to sleep. Over the past week, he will constantly wake up throughout the night. He only falls asleep when I’m holding him but immediately wakes up when I put him down in his crib. This cycle goes on for most of the night. It is exhausting and I feel like my poor little one and I are not getting enough sleep.

Anyone else deal with this? What helped?