I NEED HELP WITH MY ACCOUNT!

Hello, I have a serious problem with my account within the CSO server!

Today I played 2 hours ago on the server, and a moment ago I wanted to enter the server to play again but it asks me for a password to log in...
Someone has entered with my name and registered without me knowing!

I didn't mention it, but my server name is "DeYMixX".

I really don't know what I can do, I'm shocked and scared because I would like to find a way to recover my account, I'm a Steam user, I've always logged in with my Steam account. I dont know that the account could be registered, about 1 month ago I started playing and I had no idea...

I would like to ask for your help please! I can provide the information required to confirm that the nickname mentioned is me.