Pumping Question

LGalipp19

I am a SAHM and my DD is almost 6 weeks old. I'm trying to build a stash of frozen BM because I might have to have surgery in a few weeks. The problem is, I think I'm only making just enough milk for her. It seems like when I pump, there isn't enough for her to eat regardless of whether I pump before or after I feed her. I'm already doing Fenugreek etc. Im getting no where because I end up having to give her the bottle I just pumped because there isn't enough milk for her.
My second question is that when I have this day surgery, will my supply go away if I'm not feeding her or pumping for almost 24 hours? I'll try and pump as soon as I'm awake enough when I get home. Any advice would be appreciated! I would love to be able to pump at least a 2 oz bottle a day.