So what happened is Dawnguard was coming out when I had to go to my brother's, so I plugged my memory unit into his Xbox, and downloaded Dawnguard. What happened is that when I tried to load my saves on my brother's xbox, it said " Error Disc is unreadable." I was confused because the disc was fine, and was also installed on my xbox.
I tried to un-install Dawnguard and load the saves,(back on my xbox at home) then I tried to clear system cache, I tried other discs, I even cleared the game's cache. Something weird happened, I rented another disc to try to see if it worked. It did, BUT my disc then worked too. It only worked for a few weeks. I have contacted bethesda, but the representative blamed it on my xbox.