Milk Intake & Breastmilk Rant

My LO is 3.5months and is taking 170ml every 3 to 4 hours. She is no longer taking any night feedings so about 6-7 feedings in a day. She is on mixed feedings since birth. For some reasons, my LO's weight seems to be increasing quite a lot. She is 7.7kg, but her height does not seem to have increase much (9cm since birth till now). Am I overfeeding her? Additionally, as her milk demands increases, my milk supply remained stagnant. Now I have to combine more pump sessions breast milk into 1 feeding for her which starts to make me even more discouraged, like I pump so much but only enough for her to drink 3 feeds. It makes me very discouraged to continue pumping as I am the only caregiver (husband works in essential line) and I still have to work from home, and take care of her, pump milk and wash all the things. I feel like giving up.