My best guess would be that this score doesn't necessarily mean that you have gotten worse or that you haven't improved your knowledge base.
I also wouldn't read too much into it since you are are only doing dedicated Step study 3-4 times per week right now. Are you going to have a dedicated study period with no classes?
I will share my own path with the NBME tests and how I used the information - right before dedicated Step 1 study - 170. A week into study period - 215. Two weeks later - 220. So between the 215 and the 220, I felt like I had accomplished nothing in two weeks of studying 12 hours a day/7 days a week. So I evaluated my performance on that 220 NBME - and I realized I may have learned a lot in those two weeks, but I needed to work on test-taking skills. I was overthinking simple questions, which lead to me changing my answers to incorrect ones and wasting time (so that I didn't even have enough time to give proper attention to the last three questions in a couple blocks). I also noticed that I underperformed in my previously strong areas (mostly microbiology, and this made sense because it was not as fresh anymore). There were also a couple areas that I am admittedly weak in, like respiratory physiology and pathophysiology, and I performed more poorly in these than the test before (probably because this NBME just happened to be heavier on this weak area of mine). Perhaps the exam I took before was just very generous to me in these areas and my score was a bit inflated.
So with all of this information, I shored up the weak areas I knew I could be strong in (microbio), put myself through a bit of a bootcamp with concepts I knew I was bad at (respiratory physio and pathophys, others), and started practicing test taking skills. I focused on reading the question, going with my gut, and moving on. Timing was an issue for me, so I worked with a one minute timer to get myself in the rhythm of answering questions quickly rather than thinking too much. (another thing I realized from looking at uworld stats was that I was spending the most time on questions that I got wrong anyway. So now if I don't know it, I put an educated guess and mark it to come back and think later).
I took another NBME this past week, about a week after my 220 score, and I got a 249. I feel good about this - I saw huge improvements in what I had devoted time to, and it is consistent with other metrics of my performance, UWSA1 and 2, and the free 150.
So this is just one way of approaching the scores. I identified specific areas of weakness, and worked on them, rather than accepting that number as an indicator that I hadn't improved anything. I had improved things, but there were some barriers to that improvement translating to a significantly higher score. In the end, this is still standardized testing, which is a bit of a skill in itself. Take my advice with a grain of salt - I am just one person and I felt like my situation was a bit similar to yours. I only have NBME evidence that I improved my weaknesses, but we will see if that translates to my desired score on the real thing.
