Internet is constantly spiking/dropping

I've had Xfinity for over 3 years in my current apartment and about a month ago I started to get random drops in the day. This got worse and worse, so I bought a new modem and set it all up. Now, I have internet, but it is spiking like crazy. Streams video fine, but when playing games, I am rubber banding a lot. When looking at my connection via the task manager, the graph is going up and down like crazy. I got a new modem to try and fix this which is a Hitron CODA56, and it still exists.