Sorry but your funds was already stolen and you can't retrieve it anymore. Can you remember the software and apps that you have downloaded to your PC?
Let's say that you have been aware of protecting your security all of the time but you probably missed some random apps that you have downloaded and didn't noticed it as you use them.
it becomes very possible if he has used an app that contains a backdoor etc.
maybe this is my suggestion to use premium antivirus which has banking, payment and cryptocurrency protect features as I use it on my device
and to keep it even safer I recommend closing your webcam for secure your password
What kind of antivirus is that?
Even you are activated with premium and best antivirus but if your browsing activity isn't monitored and you keep downloading unfamiliar apps, there's still a chance that you might get a backdoor. Or there is a tendency that you might your wallet info into an unknown sheet or fill up forms.
That's the thing, antivirus only adds a layer of protection for the user, it's the users fault for downloading a shady app and doing dangerous things that could compromise his security. But still, antivirus would still be a great help protecting the users.
My recommended antivirus is just windows defender when you are using windows 10.