Working your ass off UNTIL Med school is one thing and working your ass off DURING Med school is another thing.
I was in the same boat as you are, I also had my doubts about being in Medical school, but I had made up my mind about doing it and this is one of the things that I had to seriously face : all that feeling of " I don't feel like doing it anymore, because I've worked hard to get here, but now it's not what I expected " might be just a lazy attitude in disguise. I mean, c'mon, did you really find that preparing for Med school was a party ?! I don't say that I didn't enjoy it, but the only thing that made me to get into Med school in the first place was to assume that yes, it is going to be hard work, and I know for sure that my forehead was frowning very often through the day.
My point is : getting into Med school wasn't a party and being in Med school isn't going to be a party either.
However, is this a problem ? It depends on your work ethic.
When I was preparing for Med school, I watched a lot of material made by various entrepreneurs, motivational speakers, athletes, etc. and it was very stimulating to learn about work ethic over and over again : basically the most essential idea is to value work for what it is and not try to transform it into something else - a way of saying that if you enjoy your work, that's great, but don't expect and don't be dependent of enjoyment all the time, because through work you're really testing qualities that are best tested through work, such as : persistence, patience, mental toughness, etc. - Just take mental toughness for example : you can never actually test how tough you are as long as you only experience pleasure; it simply won't happen ! Toughness is tested through challenges, period.
As one of my favorite mentors once put it : "If I walk around and I don't see that you're at least a little pissed, then I'm going to be pissed." , and his point was to not choose the "right path" based on when you feel "alright", because walking on the right path doesn't mean that you're feeling alright.
Actually, big challenges are always big discomforts - I know you said that you feel like falling apart and that you're afraid of not doing damage to yourself and to others, but think very well before you get intimidated by the difficulty of a situation, because it might just be that you're afraid of slaying a dragon that you would actually have the strength to slay.