Starting USMLE Rx Questions

I am currently in my second year of medical school and have recently just started doing USMLE Rx questions. I have been doing pretty well in my classes however I am only scoring in the 40-50% range when doing questions from this question bank. Is it normal to be scoring this low when first starting off or is it something that I need to be worried about?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums