i'll go against the grain a bit and say that i really enjoyed third year, for the most part. The long hours of surgery suck, and ob is mind-blowingly awful in so many, many ways. That said, i did enjoy surgery, and i felt like i was actually learning useful knowledge most of the year. M2 wasn't all that terrible for me since i didn't really study a whole lot until i started gearing up for step 1 during march-ish of the year. i can't say i was ever really interested in what the first two years of med school had to offer, but i knew it was just something to get through to reach my goal. (it's disturbing how much of this training i can say that about, which is a big reason i wouldn't go into medicine again, but i digress.) i totally understand burnout during m1/m2. Let's face it: Those years suck. You're just drowning in an endless deluge of mostly useless info that you'll forget as soon as step 1 disappears, but you've got to push through.
In the mean time, maybe you should lighten your load some? Chill out for a test or two. Study to pass and nothing more. Make an effort to go out, play sports, play video games, read, whatever. Do something to regain your precious humanity because lord knows that medical education is set up to strip you of it. Hang in there. This, too, shall pass.