Start here: troubleshooting guide. If you still need help, please post your equipment details (make/model of your modem/gateway/router) and a screenshot of your signal levels and your error/event log. Thank you!
Hello, Bkauff23, welcome to the Xfinity Forums!
Please review the troubleshooting guide that Nerdburg provided and let us know how it goes. If these troubleshooting steps don't help then I can absolutely take a closer look so we can get you back to top speeds again.