Sooo...only you know how comfortable you are in physics but I would definitely say that taking the MCAT befor finishing physics COULD be a waste of your time. To be sure, take a practice test and see how you do and see what subjects you know well already and those that you need to improve. It's never TOO early to start studying though. I wish I had done that. Go get a MCAT book from a book store so you can see the major topics that you'll see on the MCAT and start reviewing those topics TODAY!!!! But honestly I saw the most improvement in my test scores be repeatedly taking tests. I had the time, so I would take one test a day. The MCAT is much more a test of endurance and strategy than actual content.
Hope that was some what helpful. Good luck!!!
