Can i see when someone else is logged to my gmail account?

My boyfriend knows the password to my gmail account, he is overseas now. If i am logged in, where can i see if he is logged in as well???He said it should say somewhere something like "this account is opened at another location" but doesn't wanna tell where and he is telling me that from Gmail you can track down even the computers id of the people in ur address book and even hack their computers. is that true? Please help. Thank you

Can i see when someone else is logged to my gmail account?
No, it won't tell you if it is already logged in. I think he watches too many TV shows.