It's not that bad
I remember I was super nervous like you. But after taking it, I realize its not the end of the world. Well, you might study differently than I do, but I suggest you don't study the day of your test. I totally freaked out when I did that, and for about an hour or so before my test, I couldn't remember even the basics!
Anyhow, if you actually put honest time and effort into studying each section, you have nothing to worry about. Trust me on this
I used Chad's for both OC and GC and I scored relatively well in those sections. I didn't have time to study biology or QR, and I scored poorly on those.
And FYI, I scored a lot higher on the DAT than on Topscore exams, which I took within the week of my DAT
I usually scored 16-17 in OC Topscore, but received a 20 on the real thing. I usually scored 17-18 in GC Topscore, but scored a 21 on the real thing. Good luck!!