I need some advice! I'm EBF and my daughter did great at first but now towards the end of her…

I need some advice! I'm EBF and my daughter did great at first but now towards the end of her feedings, she pulls away from the nipple and starts screaming her head off and is inconsolable. I know its not lack of milk because she has several dirty diapers a day and is gaining weight really well, I also check by hand expressing and it flows right out. Switching sides doesn't help. It seems like she's in pain? I burp her several times while feeding but sometimes it only makes her scream more. But then she starts gnawing on her hands like she's still hungry so I'll offer her the boob and she'll frantically latch again for a few seconds and then turn and scream again. I also don't think it's a fast let down because she does it after she's been eating a while and this seems to be worse in the evening. HELP!