Advice on breast milk supply🥺

My baby girl is 3 weeks now, and her appetite is growing but I’ve notice my milk supply is diminishing before I would pump out at least 1.5oz each boob! But now combined with both boobs SOMETIMES I BARLEY GET EVEN 1OZ!! I’ve had to supplement with more formula which I kinda don’t want I want her to eat more breastmilk and a little formula. I’ve had to pump ever since she’s was born Bc she can’t latch on to my boobs she gets so frustrated when I’ve tried more than 5 times. Any recommendations I can do to maybe help my baby latch on or recommendations to help increase my milk supply please!