Windows Can't Format Disk?

SO, problem is: I got this USB, it worked very well 'til some days ago. I can't format it, no matter what I try, e.g. formatting it using different formats, formatting it using Computer Management, formatting it in safe mode. None of these things seem to work for me, and I have no idea why. There's also something else to it: before it became unusable and not format-able, it was somewhere around 4GB, and now, when I want to format it, it gives only the option to format it using the capacity of 12.5MB, which doesn't work anyway. I've tried looking at unpartioned spaces in it, but there aren't any, so I completely have no idea how to go through this problem.