As other said chances are extremely high that you have been hacked.
However what I want to add is that one should learn from it errors, this is not a problem of electrum itself but rather the user bad security in your PC. What can be done? Of course you need to install Electrum in Linux mint or Ubuntu and if you don't plan using Windows save your documents to some external big USB or HDD and format your hard disk next.
If you want to still use Windows, reinstall Windows first and then install Linux in a second partition of your hard disk. There are a lot of guides of how to divide your hard disk in 2 partitions in google.