Help! My account appears to have been hacked!

**Note: This is my son's account, he's had to let me log into this just to post this message!** So, I tried to log in to my hotmail yesterday as normal but the account wouldn't accept my password even though I know I hadn't changed it. I went to reset the password but it ask me for my mothers birthplace which I answered and it said it was the wrong answer! I know where my mother was born and i certainly have never used anything but the one answer I tried! failing that I tried to get a code sent to me but the email address it stated isn't one of mine! And nobody I know has one like it! I