and now the boss is placing orders through my account?
Good Lord! Change your password immediately!
Where are his purchases being sent? Check your Paypal account and change that password too.
You might want to record the instances of your boss doing this and have a chat with HR.
I signed in to my laptop with stay signed in unchecked and I go back to eBay 3 weeks later I don't need to sign in?
I basically only use my home computer, but I have to sign in and use my passwords on dotCA.
But on dotCOM, where I sell about half my stuff, every account fills in the password automatically.
I use Macs exclusively at home.