I am going to install a ceiling fan in the master bedroom.
There is no ceiling fixture but there are two sconce lights on the wall.
The feed from the panel is #14/2 and there is a #14/3 running between the sconce light boxes.
Another #14/2 leaves the box with the feed and goes into the light switch.
“I think” I would disconnect the #14/3 and connect the feed to the 14/2 going to the switch and running it into the new ceiling box, then run a new line to the switch so the fan could be switch activated.
If you can clarify how the connections are made behind the sconces and the number and colors of wires at the switch it would help.
It sounds like you may have a switch loop from the 2nd sconce to the switch, while the power comes into the first sconce. This would explained the 14-3 between the sconces, a constant hot and a switched hot connected to the fixture wires.
I don’t mean to offend anyone but, just like you would advise a client to seek professional help i will do the same to you. Call a licensed electrician and pay for a professional job. And so you know I am an electrician