By 'good security' I hope you meant you have a bank PIN/2-step verification on your registered e-mail address as well.
Have you recently visited youtube/twitch links or emails offering giveaways/DXPs of that sort? Clicking on such links can help hijackers take control of your account (bypass login information, even bank PINs).
You should also run a scan on your computer to pick up any malicious softwares. Changed your account and registered email passwords and apply a new bank PIN after that.