Suspected hacking—changed password

I saved my password on my computer so every time when I open up outlook.com, it automatically goes into my email account. But today when I tried to access my account online, it says "someone has logged into your account" and redirected me to change my password. But I didn't notice any change of my emails. So I suspect that my ex bf could possibly hacked my email account to see my contact activities. Or could it be possible that the IT team at work hacked into my account because I logged in to my hotmail at work? Can I find out where the person who hacked my account was located?(just generally in which state or whether in the US or not). Pls help me find out who did it.

Thank you!