"This will be the class where they will pull me aside and say, 'We know you're trying really hard, but a doctoral program just isn't for you.'"
This was part of my self talk all the way through my Ph.D. And then again when I became a faculty member. These were the latest is a long series of imposter experiences I had. Then I realized that other people (in my experience MOST other people) have had the same moments in their lives. Moments of doubt and not belonging and isolation. Moments driven by the fear of being found out to be a fraud.
So it's a thing. It's got a name. It sucks. Then gets to the point that it's not quite so bad and you think you might know what you're doing. Then you fall back into imposter mode. And so on and so forth.
Let it be a thing you navigate. And then let it be a thing that helps you relate to others. It can be a tool to help ourselves and others not just a weapon we use to beat ourselves up.