My SD card is not working properly.

Hello,
I tried uploading my pictures to the computer and none of my pictures were not viewable. The first thing that it said was "There might be a problem with some files on this device/disk. This can happen if you remove the device or disk before all files have been written on it." And it asks me if I want to scan and fix it or ignore it. I ignored it the first time and I couldn't open any files so I tried it again and this time connected it with the USB cable from the camera to the computer and I was able to view some pictures but only half of them. So I tried it again and this time putting in the SD card to the computer and choosing the scan and fix but that just made it wost because I can no longer see any pictures. Even when I put the SD card back in the camera it says that the file is too large. What can I do? I have very important pictures there. How can I retrieve my pictures?