Please help me get my facebook account back!

Question

i have been a fb member for over 6 to 7 months i have been having a problem with somebody hacking into my account for awhile, MY EX!! the problem started when i changed my fb account name and email addy, and passwords, now i cannot get into my account. how do i go about getting my facebook account! i would be grateful if you could help me in anyway you can thank you. liz