Facebook not recognising my password

Hi. I think my FB has been hacked. On my PC if I try and log in and for a few seconds I manage to get in to my account and then I get a box up asking me to log in. When I put my password in again, it does not recognise the password. When I am on my phone, I keep getting boxes up to say session expired?

Can anyone help, as I can't even get on my home page to go into the Facebook help link.

Thanks