My upload speed changed from a week ago with a new cable modem installed from Xfinity

Thanks for meeting us here in our community, @FCCJANE, about your speed uploads. I can understand the frustration since that is quite the difference. Have you checked your Xfinity app to ensure an area interruption isn't the cause? You can also use: https://www.xfinity.com/support/statusmap to check the status as well.