Cant access my facebook account

Hello,


i cant seem to open my fb account..it just completely stopped redirecting only a day after i used it.my email account isnt opening either...the password i entered on fb is detected to be an old password...although i know i never changed it!!!!my sisters can still open there accounts from the same pc....if its been hacked...then why would anyone want to hack my account??plus i opened fb at 2 am and an indication is given that your password was changed at 11:27 pm on the same day!!!!?????
pl pl help im getting really worried...