Slow let down and flow

I’m thinking I have an issue with slow flow and delayed let down. My babe definitely gets frustrated when she’s really hungry and is now starting (to what I think) just do short but super frequent nursing sessions (every 1.5 hrs). it’s like she gets the fast flow of the first let down on each side and then gives up and goes to sleep. She is gaining weight really well although slowed down a tiny bit once we started EBF about 3 weeks ago (we were supplementing/pumping a lot before that). I constantly am doing breast compressions when I nurse. I’m starting to think she’s just starting to be like “screw this” and eventually is going to refuse the breast and/or have her weight gain suffer.

Anyone else go through this or have any advice? I already pump twice a day and am now EBF so have an extra 6-9 oz a day. Should I add in another pumping session to try and increase supply?