Question about Outlook Express

I have a pc at my home in Connecticut with a hotmail account that is saved in my favorites. I am currently on my sons pc and checking my email messages on his pc in north carolina.  Can someone in connecticut be pulling up my messages in connecticut even tho i have changed my password while in north carolina. I believe a family member in connecticut is on my pc and reading my mail. Is it possible that the I left my email account page open on my pc in connecticut and they can continue reading if it is not shut down on my home pc in connecticut? If so, How can I eliminate there access while i am away? I have just changed my password but i am afraid they have left my email page continuously open and can continue to view. Is that possible?