Experiencing large amounts of packet loss

Yesterday afternoon my internet started acting up, streaming videos were buffering a bunch, webpages would fail to load at first and than go through a few seconds later, and I was getting large latency spikes in games.  I reset my modem, my router, made sure all firmware was up to date, replaced the coax cable to the wall just to be safe, reset the gateway.  Nothing worked.  I ran a test with ping plotter pro and it turns out im getting a lot of packet loss.  I contacted xfinity basic customer service and the woman I chatted with told me she checked my connection and everything was good on her end.  Any idea what I can do from here?