Yeah, either get a different study group, or just don't use a study group at all. I stopped going to meeting after my first exam and I feel that I have become a lot less stressed and a lot more productive. There's one kid i've been friendly with all year, and now when he comes anywhere near me i start to stress out. Try to surround yourself with people who don't outwardly or obviously project that kind of vibe - its really contagious - especially right now at semester's end. However if you feel the need to meet with people - try calling up one of your friends and doing it one on one - I find this to be easier, more respectful, and a lot less stressful - even though you are sacrificing a couple other opinions...
However, as a disclaimer: I am just a silly 1L and this plan may not ACTUALLY be working for me. But i am having a much easier time getting through exams now that i have seperated myself from stressful people.