Baby pulling off and crying when letdown starts

Baby is 7 weeks old as the title says she has started to pull off and absolutely lose it when my letdown starts. This doesn't happen every day, but when it does it's in the evening. She will relatch after she's calmed down but as soon as another letdown happens she pulls off and cries again. This usually happens 2-3 times in an hour and then I just give up trying to nurse her because I get so frustrated.

Has anyone experienced this? Why is this happening??