Lazy nurser

Believe my baby is a lazy nurser. She eagerly latched and sucks whil until letdown and drinks, but once letdown is done she's pull off and screaming. I burp her and try to relatch her and she'll suck a bit then do it all over until I offer the other breast.

Out of curiosity I pumped after feeding and only got less than an OZ from each breast but it was all thick white milk. The hind milk that everyone says is the prime milk. How do I get her to keep on the breast and actually suck to get the good stuff and full her belly.