I think some one has been in to my account

Hello,
I was on my lap top today checking my email and I kept getting the massage that my account was out of date. Than my computer closed down and restarted up again with the massage
''Your files will be in the same place do not turn off your computer'' Then when it came back up
i went to check my emails only to find that all my email had gone the only one's that are now on my account go back to 2015.Also all my folders are empty.Please can you help me !!!