Sleep regression?

Anyone else going through it? My 4 1/2 month is JUST starting. The first night I thought was a fluke, but he’s woken multiple times throughout the night for four nights straight and is up to eat at 5 AM like clock work. He was sleeping from 9:30-7 or 8 without waking and then bam it’s like we got hit with a tidal wave.

How long do sleep regressions usually last? This is the first one we’re dealing with.