Sleep regression

My baby turned 4 months yesterday and he screaming every 2 hours at night 😭 ! He has been a good sleeper at night from day 1. He’ll fight going to bed but once he is out, he’ll sleep for minimum of 3-4 hours sometimes 6-7 hours straight. Wouldn’t nap in the daytime unless in my arms. Now he is excessively fussy. Only sucking and or me holding him consoles him.. it is tiring . Can’t watch him cry 😭😭

We bath him twice a day, story, dark room , good feed, sleep sack, massage are part of his routine .. I let him sleep on his tummy while I am watching so he can get 2-3 hours at a stretch. He doesn’t roll yet. please help.