Internet crashing randomly while playing video games

Whenever I play video games, my internet has these massive lag spikes sometimes. I have days without any, but some nights I simply cannot do anything because my internet is so slow.

Example video (Black Ops 2:) http://www.youtube.com/watch?v=GDARckiuZP8&feature=youtu.be

My connection goes from 4 bars to 1 bar and back, and does that every few seconds. Makes the game unplayable. Also, whenever I exit the game my internet remains slow and the connection to my router remains weak instead of the usual 4-bar.

My computer has a built-in wireless connector, which is the Sitecom WL-320 PCI Card 300N. If there's anything else you need to give me a solution, let me know.