Don't worry, NBME 6 has a strange curve I think. You should do much better on NBME 7 and 8. Not sure if you saw my previous posts but I ended up with a 251 on the real deal after getting a 209 on NBME 6 about 2 months out or so. I got a 244 on NBME 8 1 month before so I didn't improve much in that last month but I'm still incredibly happy with my score. I was afraid of doing worse on the real deal compared to NBME 8. Based on my experience, I would trust the UWSAs and NBME 8.