I'm in exactly the same position as you and feel exactly the same way. Test is in two days and I'm kind of freaking out.
I had been scoring near my target score on NBMEs (240) and been doing OK until about mid-week. At that point, a lot of my friends started taking the Step and reporting back that it is ridiculously difficult (maybe because of the recent testing pool switch? idk), which has been really psyching me out. One of the things that I've been attributing to my satisfactory NBME scores is that the questions are way, way easier than UW.
Just to see how I would do under pressure, I took UWSA1 and ended up marking like half the questions (I'm a pretty liberal marker, but even this is a lot for me). Ended up getting a 242, but then started thinking about how its supposed to overpredict.
Anyways, long story short, you're not alone. From our n=3 data (you, me, and my study partner), there seems to be a 100% freak out rate in the days leading up to the exam.
I've gone through FA and Pathoma x1 and UW x1 + incorrects a second time, and I convinced myself that I could do another FA binge in 4 days... so that's what I'm doing right now...
Hang in there -- it's all gonna be over soon.