some advice needed

I am a new nurse. I graduated in December 2011, couldn't find a job for 6 months, and just started my nursing career in June in the general ICU. I am struggling as a new nurse. It's been four months since I've started, but I'm still slow and very hesitant. I feel like I can do it, but I have a lot of doubts. I thought I would love ICU, but every time I think of going to work I get anxious and very nervous. Although I have learned a lot, I just feel like there is a difference between knowing what to do and actually applying it. I don't want to put any of my patients in danger because I am an incompetent nurse. I'm trying my best, it just doesn't seem to be good enough. My educator and manager for the ICU wants to keep me on orientation with preceptor for longer, saying that I'm still slow and they don't feel that I know how to differentiate between my priorities. I want to prove to myself that I can do it and that I will be a great nurse. I just hate the feeling of not being where I should be. The thought did occur to me if ICU is for me or not? But the thought that keeps bothering me is what if it's not ICU, maybe nursing just isn't for me. Please help me. I'm so confused and stressed out. I am very thankful that I have a job, but I want to love my job and right now I just don't.