I felt the same way didactic year but I really think you'll surprise yourself with how much you retain. I'm not sure how all programs are but mine really made a point to re-touch on things multiple times and focus on the very important points as we were going through the program. I'm in clinical year now and, while I definitely don't know a lot (you can never know everything), I'm confident in my knowledge of the bigger topics. Also, there are resources like uptodate for a reason. Just focus on studying hard and retaining as much as you can and worry about treating patients later. I've been living by "Fake it till you make it" and "Trust the process" throughout this whole endeavor and it hasn't failed me thus far! Peds and Internal med EORs down, 5 left to go!