Internet connection is awful while Steam downloads

I'm usually pretty on top of network issues, but this is driving me nuts. I have a 12/2 connection at my house. When I'm not downloading anything, the internet feels plenty fast. If I'm downloading games in Steam, speedtest goes down to below 1/1. I would usually just attribute this to steam using bandwidth, but its only downloading games at about 1MB/S. My ping also shoots from about 9 to somewhere between 200-300. It's as if having an open connection with Steam just stalls the rest of the network and hogs bandwidth that it's not actually using. Any ideas?