I just completed my 2nd shift on the floor yesterday. I absolutely feel the same way. My preceptor pointed out that it's different when you don't have someone to supervise and report to because, now, you ARE the nurse. Obviously, since I'm a new nurse, I still do talk to my preceptor about changes in my pt's status, but aside from that, she has placed the pt's care in my hands.
Don't be afraid to ask questions. You won't know everything, and no one expects you to. Everyone knows that you don't learn everything in school. I have to keep asking my preceptor about the facility's policy with certain things (wound care, PICC line care, etc.) because it varies from where I did my clinical rotations.