He kept sending draw offers and repeating the same move until he won by time

I lost a game although I had the edge and the time. My opponent who only had 8 seconds left in his clock, kept sending draw offers and repeating the same move over and over. I declined his draws and tried not to repeat my moves so we don't draw due to repetitions. The weirdest thing; his clock was frozen at 8 seconds, it never changed, while mine was ticking every time I made a move. I ran out of time after I had a whole two minutes ahead of him, while his 8 seconds didn't change. He won by time! Of course, he's laughing in the chatbox. I am very frustrated! I reported him, but I don't feel the website is responsive enough. 

the 8 second thing is probably just lag but the draw offer spam+laughing in chatbox definitely deserves action

He didn't cheat, he was premoving and you were slow.

Turn on premoves
https://www.chess.com/play/online/settings