So I contacted the the ISP provider and they confirmed me that I was hacked by WiFi although Im not sure how since the SSID was hidden.
Hiding an SSID is NOT a security feature. It just keeps the casual person from seeing your network easily. Clients still need to know the SSID and that information is passed in the clear over the air. So anyone sniffing for WiFi can easily see your SSID even though it is hidden.
I seriously doubt that a hacker in China was connecting via your WiFi.
Make sure your using, at least, WPA2 with a very good and complex key. Disable uPNP and Bonjour and reboot it. If your using a Ubiquity router make sure you disable Ubi Discovery.