Do I have a problem?

I really don't want to bore anyone by the same old story of how worried I am for my coming exams. Sometimes I wonder, am I really worrying unnecessarily? I seem to be doing a hell lot more work than majority of my other medic friends, yet there's still this strong feeling of insufficiency lingering in me. It's really hardly surprising. In every other book I flip open, brand new chunks of information surface. This means that if I were to read 10 different books, 10 different books will give me different information on the same topic. I'm not even exaggerating. To top it all, the PBL method of determining learning objectives as a group from the cases just adds to the doubts about what exactly should we be learning. The unfairness comes in when some groups' tutors readily read out learning objectives provided in the tutor's casebook while tutors like ours would not even hint us if we are on the right track. How unhelpful is that?
Another issue with me is that I truly and really want to make the fullest of these two preclinical years to build up my foundation in the basic natural and behavioural sciences for my clinical years. I just have this thought that if I don't read up my stuff well, I'd be killing off patients. Sigh... How foolish of me to just have realise that there can be no such thing as 'knowing everything' in a topic.
And now, back to my usual exam time dilemma. I'm struggle to concentrate and keep my motivation high. I can discipline myself to sit with the book but half the time, I just could not force anything into my brain at all. It's really sad. I hope I'm not the only one having problem like this. And I really hope I can repeated my honours feat I accomplished last semester.
Just another unrelated complaint. I don't like my PBL group. I'm ok with most of them, but there are a few who just can't stop talking about what they themselves have experienced or heard from TV/aunt/'somewhere'. Literally half the PBL session is always wasted on these trivial, rubbishy conversations between these 3/4 people in the group. When I was the chair, I tried really hard to minimize those rubbish (especially on the second session) but I ended up making everyone feel tensed. Well, at least we've managed to make full use of the one hour session. Now I just dread going to PBL sessions because of these few people.