Boards and beyond is a good resource. Without seeing the type of question you're getting wrong it's hard to say the "best" resource to use. If you're getting pharm related systems questions wrong, use FA/sketchy. If you're getting physiology questions wrong, take a look at BRS physiology or try Physeo (sort of like pathoma for physiology). Overall, I think you just need to take a good look at the question type (phys, pharm, path, micro, etc) and then the system that it is related to and focus on that specifically.