Question for those that EBF and pump for extra supply:

My son will be 4 weeks old Thursday and has been awesome at latching from the start. I was advised by the LC at the hospital to wait about 4 weeks before I start pumping to build up a freezer stash. I feel like my supply is well established and I’m ready to start pumping, however I’m not sure how best to start. I’m so afraid of pumping and then him getting hungry a short time later and me not having enough milk for him since I pumped.

I attempted to pump a little after each feeding one day last week, but he decided to clusterfeed that day and since I had pumped I didn’t have enough milk for him and had to give him the milk I pumped in a bottle, so I got no progress in building a freezer stash. :(

How do you do it? How do I EBF and pump to get a supply in the freezer?