Fely,
It's definitely a fake. In addition to Billsfan's observations, there are a couple of problems with the jersey:
1) The cut of the collar is wrong. It comes to a pointy 'V' shape, which is inconsistent with genuine Bears' jerseys; and
2) The Bears jerseys are "bat wing" cut. This is similar to the Broncos (which is easier to see, with the orange sides on the Broncos jersey) but basically the horizontal line across the front of your jersey shouldn't be there. I believe the Bears have always done this, or at least in the Cutler era, though I'm not 100% sure.
Check the pictures of the following Forte for comparison, and hopefully you'll see what I mean with the above 2 comments:
http://www.ebay.com/itm/BEARS-FORTE-AUTHENTIC-JERSEY-REEBOK-NFL-NEW-FOOTBALL-/190559967466?pt=US_Football_Fan_Shop&var=&hash=item72179f34b9