4 month sleep regression!

Before my 4.5 month old guy would sleep about 7 hours before needing to nurse and then go back down for another 4 or 5hrs. During the day I'm nursing about every 2-2.5. Tonight he only slept 4hrs and then 3.5hrs. My issue is he's nursing a normal amount (not a quick comfort nurse back to sleep). Is this another growth spurt? Or the sleep regression? How can I break him off it? I work a 13hr shift as a nurse so I need more sleep than this!