Everything you are feeling is completely normal, especially transitioning from the floor to the ED. Prioritizing and gut instinct will be your greatest ally. Over time you will find your groove and things that once frazzled you will be second nature. One thing I have noticed when precepting is many new ED nurses tend to get anxious when a they have an intubated patient. Over time you will appreciate them as for these patients you know the airway is secure. Also when prioritizing and you have several patients "trying to die on you" remember pain has never killed anyone. It sounds cold, and it is, but when you have to pick one patient who is #1, it's not the one on the call light crying for pain medication. After everyone is safe, certainly get this patient comfortable and to a tolerable pain level. But the paint hollering, cursing and on the call light can be delayed a few minutes for someone who's ABC's are not secure.
You will get more comfortable with time, stick with it. :)