Aoden, I am very sorry to hear about all of your pictures being lost. I rely on my phone for holding many of my pictures also. First, did you get any error messages before the pics disappear? Were these all pictures taken on this phone? Make sure your phone is set to save pictures to the SD card & not internal memory. Open your camera, press the Menu icon then check the Save settings. If it is set to save to internal memory, then the previous pictures you took are on the phone's memory & not the SD card. If they were on the SD card, try using a card reader or connecting your phone to your computer to see if you are able to view your pictures that way.
If the pictures are not showing on your phone or SD card thru a computer, sadly there is not a way to recover them.