I was ready to erase my drive and reformat, but thank God I didn't give up so early.
One day, out of the blue, the grey screen with the Apple logo and spinning thing would show up while booting and just stay on that without actually fully booting. Sometimes, it wouldn't even get to the grey screen and would just turn off for no reason.
Single User mode would boot, fsck command told me Invalid Sibling Link, Disk Full Error and my drive could not be repaired.
Verbose Mode didn't work. My computer would just simply turn off when I tried booting it.
Safe Boot didn't work at all.
Target Mode with my friend's Macbook Pro opened up fine, and I could see all my files. I tried running Disk Utilities. Verifying my drive would say my computer could not be repaired and that I should erase it.
Thank God I didn't give up. I cloned my entire drive to an external HD connected to my friend's Macbook (I did this just in case I had to erase my Mini's internal HD. I tried Disk Utilities a few times, it still gave me the same message. I got DiskWarrior, and repaired my drive within seconds!!!!!!!!!!!!!!!!!!! My computer was back to normal!!!