OK, so two things are happening here.
200KB/s equals 1.6Mbps which is exactly what speedtest is saying you have.
a. You may be on a congested cable line. Cable distributes bandwidth across the users who are part of the pairing, so if all of your neighbours are connected on the same cable loop you are on the same direct network and sharing the bandwidth between you. You can test if this is indeed the problem by performing the speedtest once during a peak internet traffic time such as 6-7pm and once at an off peak internet traffic time such as 2am when most of your neighbours are asleep. If you suddenly get a drastically higher download speed at the 2am test it's congestion that is your problem and there is nothing you can do to fix it.
b. The network infrastructure you're using, such as your Ethernet over power network could be causing interference as a result of numerous factors, not least of which poor quality electric wiring. You can test if this is the case by connecting your laptop directly into the router in your living room via as short a cat5e (Ethernet) cable as you can find and running speed test again. If your download speed changes drastically at that stage, this will be your problem and you'll get better performance from switching to a WiFi connection or running actual cat5e from the living room to your bedroom.
c. You may have gone over your download limit and have been shaped. You can test if this is the case by logging into your Comcast account and checking to see if you have shaping activated.
d. Something else weird is going on, which would only need mentioning if this didn't turn out to be one of the first three.