I am publishing a book and would like advice on it. Could it get copied if I paste it on a writing website?

Anything that you put on the internet without a copyright is basically up for grabs. I don't recommend doing that. If your family and friends are too busy to look at it for you, look for people in other places. Is there a writing group at your school or somewhere else in the community? Maybe you could ask a teacher to look at it for you and give you advice and criticism.