new to pumping - please advise - how long do you pump?

Jazzyashes84

I have the medela double pump. (the backpack one). After meeting with the pediatrician and twice with a lactation nurse and doing the weigh-feed-weigh, we realized LO isn't getting enough from me. In the first 10min of pumping I make anywhere from 1oz to 2oz. Right now I'm having to supplement with a little bit of formula in order to make him 3oz bottles.

What I do now, is I turn it on and do the stimulation phase until I see milk coming out and right away I hit the let down button. Then I turn the dial to the "maximum comfort volume" for me and keep turning it up as I feel comfortable. After 10min like I said, I only have 1oz-2oz total. 

Should I pump longer?  Should I do different things within the session?

Please help /