Yosemite boot loading bar freezes at 50%

About four months ago I replaced my HDD with an SSD and just yesterday when I went to boot my mid 2010 MacbookPro up it wouldn't get past the Apple logo screen. The Yosemite loading bar gets almost exactly halfway and then stops indefinitely. I tried resetting the NVRAM and SMC and it now doesn't even respond to me holding down Alt to select the recovery drive. The loading bar appears almost exactly when the boot sound is finished. The computer also now shuts down completely after 15 minutes or so like this.

Semester starts on Monday and not having my laptop would be a pain. Any help is welcomed. I'm nearly about to put my (working on this MacBook already) Windows 8 HDD in and use that this semester.