Why is my internet service being constantly dropped?

Over the years my Xfinity has been basically okay. Occasional interruptions but nothing critical. Several months ago it began to get worse. Service being interrupted more and more often. Today it was just too [Edited: "Profanity"] much. I was watching a streaming movie while riding my indoor bike. The film was interrupted 21 times in 18 minutes, each interruption long enough to warrant the "attempting to resume" notice. Additionally, during this same time there were over a hundred mini-interruptions lasting shorter periods of time. All the while I had the same movie on my living room television, which I could still hear, and there was not 1 interruption. Suspiciously enough this serious degradation of service seemed to almost perfectly coincide with Xfinity offering an upgraded service for additional fees. If you choose to respond to this message please don't give me the standard Xfinity checklist of things to check at my end - I've already done them. I've cleared cookies and cache, unplugged all devices and double checked them when they were reconnected. If you have a response that makes sense I'd love to hear it. If not, I will be changing internet providers and sharing this post with any appropriate sites on the internet that will alert potential customers, as well as equally perturbed existing customers, to the poor service they can expect if they rely on Xfinity for their ISP.

Regards, 

Charles [Edited: "Personal Information"]