Constant packet loss when using internet

Having intermittent and constant packet loss across all devices, i pay quite a bit a month for upgraded internet to avoid this issue and it is still a problem. Constant packet loss when online on computers whether wifi connected or ethernet, intermittent issues with streaming services. Upon using xfinity for the first time there were no issues the first 2 to 3 weeks. Now it is nonstop. You would not think this would be an issue when paying for 1200 mgbps speeds. Please help.