Hi there!
Sorry to hear about what happened on your account. Based on your description, it looks like someone has changed your email address already for signing in to your Microsoft account. On this case, it is best to follow the steps on the Microsoft support page here:
This can help in you recovering your hacked account. Make sure to follow each steps on the page to get through the account recovery process. The page is from the Microsoft support page itself.
I hope the above information helps and hope you recover your account soon!