Account hacked

Hello, I bought access to PoE 2 on my Steam account, played the game for 20 hours, and then stopped playing for a while. When I came back to play, I noticed I didn't have any of my old characters, only some level 97 character. I was only playing on my Steam account, and I definitely couldn't have leveled it up that much in 20 hours. Someone was clearly playing the game through my PoE account. I logged into my Steam account and saw that the email address linked to it wasn't mine; I most likely hadn't even linked an email address to the account before. I can provide any information I know that will help me recover my account. I'm absolutely certain someone has gained access to it (I was hacked).