What should I do?

Recently, school's been a bit too much for me. Since I'm a hopefully a graduating student this March, I've been busy with a project with my friends in which our graduation is at stake. There are two parts in which they divided the task. One is for the documentation and the other is for the development. There are four of us. The three of them are doing the documentation while I'm the only one on the development side. Personally speaking, I still think that the development side is way harder than the documentation side. Though I'm not saying that doing the documentation is easy. The thing is, the development can also be divided into sub-categories in which tasks can still be divided. But I'm the only one doing it. Being the way that I am, I just accept it telling them that I cannot promise that I can finish it...but all they do is wave it off and tell me that I can finish it and we'll graduate this coming March...