S3 suddenly not reading sd card

[Aharrington93268]

All I did wad move an app to my sd card and then restart my phone. Now it won't read my sd card it tells me that it's "blank sd card or unsupported filesystem". I don't want to reformat and loose over 20gb of pictures, movies and music. At the moment I have no way to check the sd card itself as my laptop is an older one that doesn't have the sd slot or the converter slot. Any ideas? Ive tried safe mode and recovery booting neither worked.