Video call applications such as Discord, Zoom, etc. tend to show their users an inverted image of their own cameras, but send a normal image to the other members of the call.
If it was other people who gave you notice that the image was flipped, check the video settings that Discord has, most likely there is an option to flip the camera.
If, on the other hand, you are not sure if the image that others receive is turned upside down or only you see it that way, make a call with someone you trust to confirm it.
In any case, the problem is solved in the Discord settings and not in OBS