(FYI comcast rep from nashville here doing this on my Free time and I am not trained for Internet support)

I would advise going from laptop to your modem (via a ethernet cable)to see if your getting the internet at all.
If you are getting internet then reset your router and see if you can get the internet connecting directly to it (via a ethernet cable).
If you can't then you have a bum router and should replace it (comcast in most areas can setup home networking for about $100ish depending on promotions)

hope that helps man