lol.
Maybe just search for parental control software.
Was it even your IP address? (Or possibly your IP address, as they usually change for most people from time to time).
Of course, if you have a router, than any computer behind the router will have the same external IP address. If you're only monitoring your own computer, then it still might not catch things from you. You don't happen to have any evil siblings playing a prank on you, do you?
And of course keep in mind that IP addresses can be spoofed, or those people could be lying to you.