Those router "booster antennas" rarely make any significant difference. What signal strength are you showing when in a room from which you cannot connect to the Internet?
Your only solution may be to install a booster relay at some convenient point in the house. They are small and inexpensive but do need a nearby power socket.
Arn

I have used that antenna with positive and repeatable results.  Helps access our WAP in another part of our building through steel girders and concrete walls.  I use one at the WAP and one at my PC Card antenna.