4 month sleep regression; what to expect?

Leo

I'm baby is 15 weeks old today and I go back to work next week 🥺 my son wakes every 2hrs to nurse and I'm wondering what should I expect during the sleep regression?? At 12 weeks he had a few days where he woke up every single hr and I'm praying that was his "regression" since I read it could occur early but idk and I'm scared lol

What did y'all experience?