So there are 2 sets of wires coming in on the right (black, white ground) and 1 set of wires going out to the left (black, black), which seem to connect to the next room.
When I change the switch, I ran the 2 right black wires to the dimmer switch. It works for that light, but the lights in the rooms to the left will no longer turn on. I even put back on the old switch (not a dimmer, just on/off) the same way it was and the lights in the other rooms will no longer turn on.
I am unsure what is going on here or how to get the lights in the other room to turn back on after the switch is replaced. Could really use some help.