I can't log in on facebook

Hello
Today when i was trying to log in on facebook they said that the security code was send to your mobile phone,they send me the cod but when I write this cod so i con log in they said that the security code is incorrect.I don't know what to doo.When i wanna crate a new FB account they always log me off and when i try to log in again they said me the same that write in my old facebook so i can't have a facebook profile.What i gonna suppost to do?? Help me please.I'm dessperate.Can you answer me today .This is the six time that this happening and i can't anymore