My supply is low! :/

Syrena • 25 years old. Excited for 9/13/19 💏💍. Mama to my rainbow baby Addison Meree 🌈.
Hey ladies, I'm currently working on breast feeding my little girl. We were on formula half time but I'm ready to give it up completely now that we have gotten a relatively good routine going. My milk supply was awesome last week, I was producing probably more than needed but this week I'm seriously lacking. I had to change my diet (not sure if that has anything to do with it) but since then I'm barely producing enough for half a feeding. How can I get the supply up? I've tried power pumping and I'm taking post Natal's for nursing mommys too. Any other tips?