Why is my New Desktop so Slow?

wireless won't work in your situation well without high expense
run a wire.

your problem is that the electromagnetic field your router is putting off is getting baffled by the walls and floors of your house.

I don't have a long enough wire for my room.

Also, my router never acted this bad when we first bought it. We even tried putting a foil tent to help, but that didn't last long.