you should change now your email address and password, If ever you are the real owner, You must contact the user that your account contacted for trading and attempting to scam. And better to prepare the sign message to claim your account so that mods can verify the real owner of this account. This case is made me confused because it can be a product of 2 scenario;
scene 1:
OP can truly try to attempt scamming other people and posting this thread as escape route away from.
scene 2;
OP's account really hacked and hacker intentionally didn't change password so that OP itself and the other user he trading will not be suspicious.
I'm trusting now the investigation for those detective user, My brain can't contain this kind of mind blowing situation.