Why do you think someone has the same email address as you?
Are there signs that you account is compromised and being used to send spam? If yes, change your password, enable 2 step logins, and check all of your account settings.
If you are receiving email that appears to be for someone else but using your email address, maybe someone bought a bad email list, or maybe someone accidentally (or not) used your address when signing up for something.
Are you seeing an email address that doesn't belong to you when you go to the Hotmail home page?
What a little more detail I can help provide a better answer to your question.