I'm writing books for a living. But with the arrival of chatgpt, I'm scared that anyone can write a good book with chatgpt and flood the market with good writing, making my competition much bigger. Should I be worried?

No. As it presently stands AI can’t write a decent story more than about one page long - and even that, only on a very good day. More than that and it starts repeating itself and/or descending into trite cliches, because really all it is is a cliche-regurgitator. All it has going for it is good grammar.