Baby not drinking enough formula

Dee

My little girl is 4 weeks and won’t take feeds more than 2oz as she falls asleep and refuses anymore if I wake her, she just spits it all back out.

When she was weighed this week she’s dropped from 50th percentile to 25th so I’m obviously now concerned that she isn’t get enough milk and am really worried about it.

Has anyone else had this, do you have any ideas about how to get her to eat more?