Yes, if you configure a wireless router as an AP, you connect it LAN to LAN so that would leave you 3 available LAN ports for wired connections on a 4 port wireless router.
would i need to connect the access point to the router via ethernet cable to achieve a wired connection, as i am wanting to have a wired connection in my bedroom but my router is in my living room on the otherside of the house.
Yes, an access point needs to be connected with a cable or through powerline adapters if that is not possible. But if you get a router that is dd-wrt firmware v24 capable, you can set up a client bridge like THIS if your signal is strong enough at the point where you place the bridge.
ok, could i buy a switch and use this to get a wired connection on my PS4 if i plug the switch into the access point to gain more ports and then run a ethernet cable from switch to PS4
You could connect the switch to the network with Ethernet and then attach the AP to the switch.
It would be cheaper though to just buy a TP Link wireless router, set it up as an AP, and connect it with an Ethernet cable that would leave three available Ethernet ports (the 4th LAN port would be used for the connection to the main router).