The internet currently doesn't work with my laptop. It is incredibly slow and often won't load the page or times out. Basically it's unusable. Every other device in the house works, including another laptop, a desktop, and the Optik TV box. Even stranger, my laptop works on other sources, such as when I tether to my phone or am on a different router. It is possible my computer has been attacked but it's just getting in through the one door, while leaving my other devices unharmed?
If the other computers work as expected when connected to your router, the problem is not with the Internet connection.
If your laptop works as expected when connected to other networks, it is not the laptop itself. It is unlikely your laptop has been compromised if the problem is on your router only.
A few questions:
Have you rebooted the laptop?
What happens when you connect the laptop to the router by ethernet cable?
Have you deleted and recreated the network connection for the laptop on your network?
Have you rebooted the router / modem / gateway?
Have any modifications been made to the gateway regarding the laptop itself? It is possible to restrict access to the gateway by MAC address.