There's a good chance that's problem. In order to see any affiliate earnings you need to go to your account, go to "affiliate settings", and make sure you have the correct code entered for each affiliate (which you get when you apply, and become accepted, as an affiliate). If you already have an Ad Sense account you would use the code you already have.
Another problem (if you haven't looked at your Google account to see whether this is the case or not) could be that you've earned but haven't reached the $100 minimum. If that's the case, though, it should show up if you go to your Google account.
When you apply to have an affiliate account on here, each affiliate's application will ask for things like your name and address, payment method, etc.; but if, by any chance, you haven't completed that kind of information, that could be the problem too.
If you don't have "all that many" Hubs there's a chance they wouldn't earn a whole lot, so have you linked to them from your other sites to get outside traffic?