Is my mouse too small?

I had similar problems and couldn't find a good fit until I found this http://madcatz.com/. I have the R.A.T. 7, I believe, and although it is a strange beast once i got it adjusted to my hand it is all I've used for gaming. I am not sure what the current model is that directly replaces the 7.
 
Most definitely it depends on you and your hand size. But i did have the same issue where my wrist would hurt and felt like it was going to lock up but it ended up being i was straining my wrist/hand to fit the small mouse. I upgraded to a larger one and bought one of those gel pads that go underneathe the wrist and the issue went away.