That might explain your situation to some degree. When I was an undergrad, I was pre-med.... but my major was in public health at that time as well. However, I tried to stay away from most of the other pre-meders as I couldn't deal with their uptight and backstabbing ways (not everyone, but a lot of people I knew fell into this category). Nearly all my undergrad friends were public health students, as I really liked them... even the public health pre-med students were pretty decent. But when I would take upper level science classes outside my major, like molecular biology etc-- I thought my classmates were kinda scary. (I saw many of them thrilled when fellow classmates did poorly on exams, and would do things like make intentional mistakes on notes when asked classmates asked to borrow their notes.) I know I'm generalizing here, but I personally found the students majoring in the biological sciences highly cutthroat. I think when people get into med school, they generally tend to be a bit nicer... many of my friends in med school are quite decent folks. I think it's just worse during those pre-med years. And since pretty much everyone in your program is competing to get into med school, I guess you are in the same dynamic (even though they are grad students). I'm just guessing here, but perhaps your classmates are even more strung-out because most of them have actually taken the trouble of doing a masters as a stepping stone into medicine, so maybe they are even more cutthroat than the biology pre-meds I knew.
Sorry about that. Just get through your program somehow, and hopefully your friends in med school will be a lot more supportive (hopefully they will have resolved their issues by then).