Insert a Disk into Removable Disk USB Drive Error

My USB drive initially worked fine (I can access the files and all) but then there was a pop-up saying the drive needs to be repaired. At first I ignored it as I needed to save some files, and there was no obvious problems. I disconnected and reconnected the USB drive and it was acting normally, but the pop-up came again - this time I agreed to have it scan and repair (I'm using Windows 8). However, when I tried that, it failed, and from that point on, I couldn't access the files within the USB. Heck, its name doesn't show up and 'Removable Disk' takes its place. If I try to access this'removable disk' I get the following error message:

Please Insert a Disk into Removable Disk [drive letter]

and the properties show that there is no memory used nor is there any available. Can someone, please, please tell me how I can recover all my files from it. I'm begging you, there is so much work on there I do not want to lose - ranging from word documents to .psd and .ai files for adobe photoshop and illustrator. I'm in full panic mode. Any help will be dearly appreciated