My terrain has dissapered leaving only plain colored boxes on any room I go to.
This is now all I see.

Make sure you're not on minimalist mode. Options > activate minimalist mode. Check if it's on. :p

Thank you that fixed it, I don't know when it got activated.

In the same options you can disable "automatic optimizations". This option changes your settings depending on your game's performance and can enable that minimalist mode itself.