Either my camera moves/changes size or my scene does... But why? Unity 2D

So I'm very new to unity and I've just been following along with tutorials to create some simple 2D games and on my first attempt with Unity 5.4, 5 days into a project my entire scene changed. It seemed like my camera had changed size or moved but when I adjusted it and moved it back everything in my scene was out of place- like that too had changed.

Gave up on the game and just assumed it was a bug from such an old version of unity.

Fast forward to my next attempt (with unity 2019) and the same thing happened again. I started a new project, placed background and objects in my scene and placed my camera in a good position and then went on to coding some collisions. I went from VS back to the scene and it was completely different (the camera size had changed, and when I moved it back and adjusted it the scene no longer fit in the same way). I've made no code that can affect the camera, I'm nowhere near the scene editor when this occurs- and it seems to just happen without the option to CTRL + Z.

Any ideas? This is the first time I've been motivated to commit myself to game development and this is getting so frustrating that I want to either quit or find a new engine without this problem.