Problem unlocking my Facebook account

I committed a mistake when entering my password, and FB keeps sending me opening codes that do not work. Also, they ask me to change my password, and when I enter a new one, it does not work. They are driving me crazy. I have been trying to solve this problem for two days. They also tell me that I have been entering too many passwords and that they locked my account. This happens when I try to have my password changed and enter a new password. Then they ask me what is the last password that I remember been used. At this point, I do not remember what was the last one. Please help me!!!!