Hi!
I was where you are 6 weeks ago so I know how hard it is. I was expressing 2.5-3 hourly during the day and 4 hourly overnight initially to get my supply going and after around a week went to 3-4 hourly. I always kept pumping until the flow started slowing down. I found that by doing this my supply increased quite quickly. Just looking at my records and day 5 I was getting 40-60ml a session and day 6 60-90ml. By days 9-10 I was expressing 800ml(ish) a day and I tried to hold it fairly steady around that mark (so started stopping around the 100ml each time as I didn't want to increase much more than that). Make sure you store it well. I literally have litres and litres in my freezer from those few weeks.