Growth spurt

How do I know my baby is getting enough to eat if she is going through a growth spurt. My baby is 7.5 weeks and started to be incredibly fussy and irritable throughout the whole day. She's wanting something in her mouth whenever she is fussing and I've been using a pacifier to try to soothe her. I'm sticking to feeding her about every 2 hours unless she's not able to be calmed with any measure. She's gained a great deal of weight already but I just don't know.