High ping spikes and random wifi drops

Hi, 

I've called xfinity support multiple times and each time people have given me either useless information (telling me that restarting the modem or router will fix the problem). I've tried restarting, wiring with ethernet, replacing the coaxial cable, and replacing the modem. My wifi didn't have issues a few weeks ago. I'm guessing this has to do with the server load due to everyone being home (I live in Seattle), but it's ridiculous that Xfinity keeps giving me clearly the wrong suggestions. Is anyone else having this problem and is there any in-house fixes I can try?