MacBook Pro doesn't recognize external HD for Time Machine.

Im running a late 2010 MBP 15" 2.8Ghz i7 on OS 10.9.2 I have a Seagate external HD that I attach through USB. I usually back up every week or so.. or sometimes Time Machine tells me its been (x) amount of days since my last back up. All I do is plug it in an plug the MBP to the power cord, and the rest is history.. I've been doing this for years.

The other day I went to retreive my laptop, and the back up failed. It didn't recognoize my HD?!? Not only that, it doens't appear in the sidebar of my Finder anymore.

I have run a Verify and then a Repair on Disk Uility.. (for some reason, the HS shows in Disk Utility, but not under the original name I gave it).. I even tried to REFORMAT the drive.. and it didn't work either. I also DL'd the NTFS for Mac.. I guess it's a Driver for the Seagate drive?? It didn't work either.

Does anyone know anything about this? I've tried looking under a few discussions, but couldn't find someone that had exactly my problem.

If this can't be fixed, does anyone recomend an online back up? Something that works like Time Machine. I've used Time Machine a couple times.. once for a corrupted HD, and it worked beautifully!!!

Hope someone can help!!!