My picture box suddenly changed

Starting last week, my video picture suddenly changed. A green bar appeared on the top and my picture is greatly compressed. Instead of full head and upper chest, only part of my head shows, clients say. I have to push my desk chair as high as it can go and then push way back from the computer in order for my full face to be seen and not appear to be very, very close to the screen. Apparently it isn’t something to do with my camera. Nothing has changed on either Zoom or Sessions. Client videos haven’t changed. I haven’t made any changes that would cause this. I’m on Chrome on Windows 10 and always have been. I’ve searched the Help menu and the Forum but don’t find anything addressing this. What can I do to revert back to my video as it was previously? Thanks.