I would say you are ill. And not a fraud. Here's why:

Looping obsessive thought brought on by an outside catalyst.

In this case your catalyst is being told you're a fraud. And you can't say that you are, but you feel you are, so now you must research endlessly to find out if you are.

This is not the action of a fraud. Perhaps the action of an ill person who would like to know they are not ill, even if that means actually being a bad person for faking.

I've been gone for a while now and this was happening to you all those months ago. So, this to me is yet another sign that even if your Dx was not the one you had originally, you still operate as a person like me. And I do the looping anxiety driven research and search for answers, too. Especially in stressful situations.

I don't think you're the cat. I think you're more like a rat in a Skinner box, and this jerk put you in a box with a button (calling you a fraud) that both electrifies the floor yet also gives you food. So you have to keep shocking yourself to get fed, but what you're feeding is anxiety.