Is he cheating?


You can and should report anyone you suspect of cheating. Even if just one game, you are suspicious of, then you should report it:
https://support.chess.com/article/209-how-do-i-report-someone
Reporting someone means that chess.com Staff will look into it and decide for themselves if the game was fair or not; reporting someone doesn't instantly mean they are banned.
Also, for future reference, discussions of cheating in the general forums is not allowed, but you can discuss cheating in this club made for this purpose:
https://www.chess.com/club/cheating-forum