Someone has hijacked my facebook account 3 times in the last 3 days what can I do?

In the last 3 days some @**hole has hijacked my facebook account 3 times I was able to change the pword the first 2 times to a high security pword but this time I've reached my maximum number of pword changes and they are curently in controle of my account. I know I'm not falling for a phishing email and a 24 character alpha numerical code should be too much for a pword auditor to solve. So how the heck are they getting on to my account and changeing all my details? What should I do to stop them?