Breastfeeding struggles

Hello mamas,

My baby is currently 3 and half months old. I been exclusively pumping because she won’t latch and does have a minor tongue tie. My supply is just enough to feed her but I wish I was making more. I’m getting 4oz each time if I’m lucky 6oz sometimes mainly at night pump and my very first pump. I have what I search is “elastic nipples” which makes it so hard to find the right flange size. Some research suggested silicone flange so I order the legendary ones and saw no result almost made it worst. I have the mortif Luna pump. Any advice?? Should I invest in buying a different pump. I already do integrate a power pump, pumping every 3 hours (except after midnight is my last pump until like 5ish am), eating oatmeal in the mornings, and drink a gallon of water a day.