Graphics won't wide screen

Hey, I have been playing the Sims 4 on Twitch, and as such I have the game graphics set to their resolution of 1280x720. The monitor it plays on has a default resolution of 1280x1040, and previously the graphics dealt with the discrepancy by having black bars on the top and bottom of the screen to scale it properly. Recently, I decided to check into windowed and fullscreen windowed modes to see if they would work any better for me but they didn't so I reset my graphics back to fullscreen 1280x720. Tonight, I opened the game and the black bars were gone, the game is now stretching to fit the desired resolution to the screen. Is there any way for me to get my "wide screen" mode back with the bars? Currently my quick fix is changing the resolution on the monitor itself, but it's not ideal obviously to have to go back and forth on my screen resolution whenever I go in and out of the game. I have tried playing around with the graphics settings in the game but can't seem to figure it out.