Check your outbox. It seems you sent several phishing PMs.
Thanks for clarifying
But, I am unable to see my sent messages ( outbox ) as it shows an error message with "You are not allowed to send personal messages" as I am banned. I didn't bother to check my outbox from around a year as I have not sent PMs to anyone here from long time if I can recall correctly.
If this is a case of my account getting hacked and the hacker trying to send phishing PMs from my account to get it banned, what could be the best way to resolve this quickly ? I can sign a message from my known address here if that could help.
Also, can I request to see the phishing PMs the hacker was trying to send from my account, it seems to have added more curiosity around this for me.