I think my account has been hacked

per 

https://help.ea.com/en/articles/star-wars/star-wars-the-old-republic/swtor-on-steam/ 

so just by logging in and playing via steam 

however if the swtor account is linked to another steam account or the steam account has another swtor account linked it will fail 
previous linkages need to be removed which is done in the swtor account that forms the linkage

How do i link my steam account to my SWOR account?. It wont work 

What is the account displayname ? can seek to have the account locked until you can call to regain access to the account

Hey Goffey89​, 

Sorry to hear that someone else might've accessed your account. 

If the account credentials have been changed and you can no longer access your account, you'll want to contact the support team, and they'll work with you to regain control of the account. 

Once you regain access, it might be worth setting up a security key for that added layer of protection.

Let us know how it goes, thanks!