I feel your pain! I've been at or around the same on the first 4 NBME's even tho I've been studying like mad! The good news is I'm passing, the bad news is I've around 450 on each exam, and I can't break into the 220s! With only 2weeks left! I have no idea if it will work or not, but I'm focusing on my weeknesses for these last few weeks, and then will simply take the last three days of studying to do random uworld, robbins, and first aid questions.
Good luck, and if nothing else, know you are not alone.