Go to "My Account". There should be a link to it on the top right of this page. You might need to sign in again.
Then, click on "Settings". Scroll down to the bottom, where it will say "Legal Agreements & Contract". If you're under a contract, it should be there. That'd tell you when it expires. For termination fees that might apply, check here: http://forums.xfinity.com/t5/Customer-Service/Early-Termination-Fees-ETF/m-p/2892662#M122311