Code is displaying all over

All of a sudden when I go into my theme editor the entire code for my stylesheet is showing up in the theme description and is in the sidebar where my files for my theme are. If I try and click on the index file for example it gives me an error that the URL is too long for the server (it’s pulling all the code from my stylesheet). This is totally strange as I haven’t changed anything in WordPress and in fact haven’t logged in for awhile. Last time I logged in the theme editor was working just fine and I didn’t have any errors…. any ideas on what’s causing this?