Hospital bag /diaper bag/ nursery

Kiara
Hey ladies,
I'm pregnant with baby #2 being that I'm high risk I know that my doctors will try to get my labor started early that's what they did with my first child. I wasn't really prepared I waited until the last minute to pack I forgot things and all so: 
 
I was wondering when did you pack your hospital bag? What would be a good time to pack my hospital bag? 
Is a diaper bag really necessary for baby? Or should I just bring one to be able to stuff the bag with the goodies from the hospital? 
With my first I was in labor packing an I wasn't completely happy with the things I brought. 
Please feel free so share some suggestions. Like when its too early? Or when is the perfect time. I just want to be able to pack all that I need with me being calm and all that not rushing you know.