Increasing supply question:power pumping and increasing supply when baby isn't transferring a lot of milk. Finally traveling 3 hours tomorrow to see someone about my daughters lip tie

Does anyone have advice on how to power pump? And also do you pump before or after nursing if you need to supplement?

I think my supply is dropping a bit. My daughter isn't a very efficient nurser. A nurse at the lactation center mentioned a lip tie last month even a slight tongue and cheek tie (not severe like lip).. when mentioned to pediatrician he blew it off. But we are still having issues. My daughter doesn't transfer a lot of milk and that's when I knew I didn't have a low supply. I need to try to up my supply once again just in case. If she does have this procedure and it helps, I need to try to have enough milk. All this time I didn't pump because her doctor told me not to. He always made it seem like she just can't gain with my milk. im praying this is going to help.

Any other advice about increasing supply when baby isn't too efficient at transferring milk is welcomed please.