Should I change my job?

I am seriously thinking about this question. The more I am with this department, the more I don't like the job. The worst is the director, too pushy and want things fast. My colleague is going to give birth in Nov. That's the worst part for me here. I still don't know a lot of things and yet have to cover her duties. I don't know can I manage or not. I think I will break down every day. I couldn't take the pressure from the director.. I really feel like tendering my resignation now. Don't know what should I do….Anyone can help me out of this……...