Night cluster feeding is TOTALLY normal. Mine usually did at least 3 hours straight every evening for the first 2-3 months at least. My first was a 36 week 4 day preemie. She once nursed 7 hours straight with burping and changes then nursing the . Whole. Time! I almost lost it!! That was 4 weeks.
Toss the formula and nurse your baby. You will make it through. When you breasts feel empty is when your body gets the command to make more milk. Let him feed and you will make enough. Good luck!!
Proud Mama to Hannah
(7/03) and Lily
Happy to be again after a bit of a break