Unfortunate things happened

Two three days ago! I  logged in and I saw a new msg came from a stranged id profile, with no name(it was some alphabets only-like for eg. asdferwfg). I opened that- It showed that wrong profile id and it has been deleted, Thereafter It was not normal logged in for me, my PC became very slow I could not open my chess.com profile normally, and was not able to see the chess pieces, and not able to see friend's avatar(photos) in my home page. Now there is no tab of "alerts", "friends", "games and players" "chat rooms and rcheives" tabs are checked in boxes. while I play live chess, even after formatting my PC, but my setting showing at t.

Ultimately I had to formatt my PC and then loggin now.

Plz can ANYBODY REPLY this "why it happened?" Was it an attempt to hack my password? etc.etc.

Plz halp me what to do if it happens again....