The pressure and duty of a leader

As I am a class leader and also the leader of cleaning education class, sometimes I really feel pressured and that really makes me exhausted. To be honest, I am a man who always makes myself so confused, and I usually give a lot of thought on all the issues in my live. Now I am quite wondering whether it is good for me or not.
You probably don't understand what is the cleaning education class. Let me explain it. Actually, it is a class for freshmen to clean our campus and I am their leader who instruct them to divide into several groups and supervise the freshmen when they are cleaning. But recently, I have faced a lot of problems, and they really bother me a lot. I meet almost the same problems on both two sides, the class which I belong to and the freshmen's cleaning class.
Everyone is an indivitual and people are different in many ways. As a result, eveyone has varied emotions and the ways that people think are also quite different. This is the reason that makes people only care about themselves. People become selfish and they don't care much about other people's feelings. And I am the victim under this kind of circumstances. When I am busy at working on the students issues, for examples, I have to hand in the document which needs everyone's signature before Friday, and I got those stuffs on Wednesday. I only have three days to finish it, and the difficulty is that everyone has taken the different classes, so we only have few classes that require every sophomore to take part in. It is hard for me to finish the job and there is even someone who always like to skip the class, so I cannot find him or her in the classes on Wednesday, Thursday, and Friday. In order to finish the job on time, I have to make a phone call to ask him or her to come to the class. The same kind of situation happens in the freshmen. The only thing they care about is when they can leave, and if some of them finish their own areas, they just talk to each other and never help other people. Unless I ask them to do so, and they will do it reluctantly. But they don't give the thought that everyone cannot leave until all the works are done. If they can give others a hand, then everyone can leave earlier.
Now I am really thinking about myself. Of course that not everyone is so selfish, there are still other people who are willing to help and to stand in other's shoes. I really hate those people who only care about themselves. I am wondering that if the same situation happens again, I will leave those selfish people behind. In order to finish the job, maybe I should make myself a little bit selfish to those people who don't care about others. I shouldn't always be a nice guy, after all, I am not the great Jesus Christ.