Connection to modem sporadically dropping, customer support can't fix it

A few days ago, my normally stable Xfinity connection to my modem started dropping a few times a day, for a short amount of time, maybe 5 minutes. This morning, it is really struggling. I have tried all the usual stuff, powercycling the modem, having customer service refresh the connection on their end, even buying a brand new compatible modem. Problem still persists. At the point where customer service is more interested in selling me stuff than actually helping me fix the problem. I am worried that it might be something like Xfinity is oversubscribed in my area, which is a huge problem because I don't have any other feasible options. Please help!