HELP!

My son has been the greatest sleeper since birth. At 4 months, he began sleeping through the nights (10-12 hours straight). Our routine has always been, book-milk-bed. Sometimes he’d fall asleep while drinking his milk, other times I put him in the crib awake and he’d put himself to sleep without a problem. He is now 19 months and for the last 2 weeks, sleep has been hell. He takes 1 nap a day, I bring him in his dark room on a rocking chair, give him some milk and put him down in his crib for a nap. Typically his naps last 2-3 hours. Recently, he began waking as soon as I put him in his crib and crying. It’s not a regular cry, it’s more of a screaming cry. If I put him down awake, the same thing happens. It takes 2 hours to put him down for naps and bedtime now and I’m loosing my mind! Any advice would be appreciated