My pc has 1 HDMI port on the gpu and 1 HDMI port on the motherboard can i plug my monitor into the HDMI port on my mother board and oculus rift into the gpu?
If you plug the monitor into the motherboard, it's running off the integrated graphics. First off, that may actually be disabled with a graphics card installed (depends on your motherboard), and secondly it would ruin performance in non-VR games.
I'd recommend getting an adapter so you can plug the monitor into eg. a Displayport output on the graphics card.