I am also having a rough time of it. I originally went to med school thinking I'd most likely end up in IM (specifically either geriatrics, cardio, or ID). Now that I have completed my IM rotation, I find myself very disappointed by the entire experience...almost enough to cross IM entirely off the list. This was a pretty big shock to me.
During my first two years of med school, I was always the student saying "no way in hell" to all things surgery - yet I have been learning more, doing more interesting things, and feeling like I'm finally "at home" moreso on surgery than any rotation thus far. This has also been quite a shock. I'm only about a month into my rotation, so I can't say for sure, but I've finally gotten that *feeling* that everybody keeps talking about - you know, the one where you get excited by what you are doing?