Devices constantly dropping internet connectivity

Ever since Comcast/Xfinity rolled out an update that was supposed to increase our internet speeds (maybe 3 months ago or so?  I no longer have the message), multiple devices in my house constantly lose their connectivity to the internet... all are using wireless connectivity.  My wife's laptop is only able to connect about 50% of the time suddenly, my tablet loses it's connection every few hours, her tablet does the same, and both our phones are constantly dropping and re-acquiring our wifi network.  I assume this is related to the 'upgrade' that was pushed out to my combination modem/router, which is a piece of gear Comcast provided.  Is anyone else having this same sort of issue?  Aside from requesting a new replacement modem/router or getting my own, I'm not even really sure how to troubleshoot.  The last time I tried with an Xfinity rep, it was almost an hour on the phone only to have the chat session terminated by them because I hadn't responded to something within like 60 seconds even though they were radio-silent for over 10 minutes while supposedly doing remote checks on my modem.