Connected to a router or to a specific computer? Sounds like the latter. That is a very unusual network topography. Usually you would connect all devices to the router. Then a) any computer on your network should be able to access the printer, and b) you wouldn’t have this weird double IP situation. Essentially right now you are using your computer as a second router (which is possible, after all routers are computers that are just running a routing application).
I’m curious, why do you care what the IP address is anyway? Sounds like you have an actual application where you need that number, which isn’t something I’ve ever needed.