Try the OOKlA speed test... Time Warner has one similar on their web site, but always good to try a couple different sites not of their own!
Link I have Time Warner Cable package with the 200 Mbps and my download speed shows 235.98 and upload speed is 23.59 Mbps.
Sounds like maybe you've got a bad cable, or if using wireless the supplied router has gone bad... OR somebody has hacked into your system and using up all your resources...
Phil
