how can i tell if my log in information is used on another computer other than the one that I'm on?

Answer 1

Change your Password IMMEDIATELY.

Do it NOW before you do anything else.

It sounds like you think some-one else may have access to your user name /password.

Tell the sysadmin right now and ask them to search the log files to see if your fears are correct (Log files will have been kept and the sysadmin can search these for specific names and log-in times).