There's something wrong with your site, because when I visit it or my colleagues visit it, we see the admin Toolbar at the top of the site, and the site seems to believe that I am you and says "Howdy, <your username removed>". Luckily, it is asking for a password for access to the Dashboard at least, but still, this is not normal for a site.
So, the reason your stats aren't being recorded is that for the past 2 weeks, Jetpack Stats have thought that you were logged in, for every single site visitor, and by default Jetpack won't track visits from logged-in users.
As for what is causing this issuem I do not know. I suggest turning off all your plugins, and if the admin bar disappaears then you know it's a plugin's fault. Then turn them back on one by one until the admin bar shows up again, and you'll have your culprit.
Alternatievly, there may be something wrong with how your theme is coded. You can try to switch to the default TwentyTwelve theme to see if that fixes it; if it doesm then you know your theme is at fault.