That is crazy dude. Congrats! I took a a look at the site and it has great traffic.
Personally i cant tell you why your getting so many users
your site doesnt look to even really be SEO optimized.
The url name does present some type of value
maybe the q2a network has been providing you with traffic?
you have google analytics installed right?
I saw some google code on your site, but didnt look into i particularly
Analytics should give you insite on your traffics source, where they found your site, where they are, etc
I did notice though that you have some pretty quality question on there
did you make some of them yourself?
that could be the cause of some of your traffic
anyways, good to hear a good success story on here
I notice you tried to install some ads on your site already
Chikita is a pretty good provider, payouts arent the best though.
good place to start until you get some experience and apply for a more major ad network