Can your IP change without you knowing?

Answer 1

yes it changes every time you dial up or if you have dsl/cable it can change at random times or when your connection resets

if you want to have a static web address to get to your ip address try a service like dyndns.org

Answer 2

Your IP does not change by itself

but there are some programs that gives you an IP every time you connect to the Internet

Answer 3

Yes, its called dynamic ip addressing. A dns server issues you a ip address in time blocks. When the old ip expires, you are issued a new one.