First Timer..HELP!

My LO is almost 2 weeks old. She is my 2nd but my first for breastfeeding. I am VERY new to this and I feel as if I'm crashing and burning. She's exclusively breast milk and refuses formula which was our plan. Sometimes she latches directly other times I pump. I have been producing less milk these last two days and I am worried. Normally when pumping I can get about 5 oz each session but now I'm barely getting 2-3 and she eats 3 oz every 2-3 hours. Idk what I'm doing wrong or what I can do fix this