One question I have for you is when you say want to devote your career to "this subject", are you referring to cognitive science in general, or to your specific dissertation topic. If it's the latter, you will probably need to rethink your goals. People generally pay you to look at topics of concern to them; even academics must please the people controlling the grant money.
You also say you came into this field from another, and that you feel you've been limited by your lack of relevant background. However, you earned a PhD in the field and managed to land three post-docs, so that lack hasn't been fatal. In some ways, in fact, your background can be an advantage because you aren't encumbered by the implicit assumptions in the field that others might be blinded by.
Your statement about having "lots of interests" suggests that you're being pulled in multiple directions, and are therefore unable to advance in any one of them. You need to decide which interests are most important to you, and determine how you can build a career around them. Also, you will probably wind up surprised by how little the specific choices you make will matter in the long run. When you make this type of choice, you tend to start figuring out how to make it work for you - regardless of what it is.
Another post-doc is VERY!!! unlikely to be the answer. Counting the one's you've already taken, you've probably been "training" for over twenty years. You know how to learn something new on your own: it's time to figure out how to get out there and put all that knowledge into practice.