Well, are you doing it to fill time? Do you enjoy the activity of spending money? Do you do it for the social aspect? Do you feel you can stop going, and stop playing the games (even the one on your computer)?

Does this behaviour worry you, or just people around you?

This is a QUIZ: http://21stepstostopgambling.com/signs_quiz.html

Here's some links I found on Gambling addiction:
http://www.gamblingwatch.ca/symptoms...addiction.html
http://www.gamblingwatch.ca/signs-of...addiction.html

If you can identify with a good portion of what is said on those two pages, perhaps it's a good indication of a behaviour that you need to change.