How to protect my hotmail account from getting unauthorized access?

I keep getting unauthorized access to my Hotmail account and I have been able to recover it using alternate email address.
I would like to know if it's possible to know who did that?
And also if there's a way to protect my Hotmail account from having the same issue.
Each time I found all my sent messages deleted, and I found one of my messages resent to an email address that I didn't recognize.
