Drying up BM and utilizing last bit

Hey all! So my daughter is in the hospital and is 2 weeks old today. We were breast feeding but stress, anxiety, and only being able to pump has started drying up my supply. My husband and I are ok with this since I was able to give her a week and a half worth, and she is on a strict weight gain schedule that only formula can fulfill. So my question is, how can I help lose my supply but still pump to relieve engorgment and use what little bit I get from that to help her tummy when she gets upset from so much formula? I've slowed down and only pump every 8-12 hours for a maximum of 5 minutes, but I try not to even pump that long. Is this what I'm supposed to do?