Struggling to get my newborn to wake up to eat

He is a REALLY hard sleeper and we were on a really good 2 1/2 hour feeding schedule for a few days and it was working great. Then last night he woke up at 1, then 5 and was up until 8. He’s gone almost 4 hrs between feedings today and doesn’t want to wake up anytime before that. Once we hit the 4 hr mark he finally wakes up on his own. I’m stressing about having him on a schedule and making sure he’s being fed enough. He is also only eating on ONE side before he is full and finished. I’m pumping every morning and normally get close to 4 oz out of my left breast and 3 oz out of my right so I don’t know if maybe he’s just getting enough to keep him full??? Like I said I’m stressing and just need motherly advice so I don’t worry so much and can figure out what I can do to.