From what I've heard, transferring to another medical school can be pretty difficult. Most schools want a compelling reason, and some schools don't even accept transfer students. Most schools only accept students if there has been attrition in their class. If they don't lose students, then most often they are willing to accept new ones. I don't know if you're coming from a foreign school; if so, transferring would be that much harder. Anyway, AAMC's website has a listing of all the medical schools that accept transfers and at what stage (second year, third year, etc.). Sorry that all of my information is second-hand, but I've also heard that as a result of transferring after 2nd or 3rd year, you don't really get a chance to know your classmates well since everyone is scattered on different rotations. I'm not sure if that would be important to you.
Have you spoken with anyone at your current medical school about your interest in/need to transfer? I'm sure they are experienced in dealing with this, and they may be able to shed some light on how easy or difficult it may be.
Good luck in whatever you decide to do!
