Q: MacBook Air 2013 only booting on safe mode after installing Yosemite

I bought my brand new MacBook Air less than a month ago, fell in love with it, all was good. It booted smoothly, loaded apps and documents quickly, and was perfect. When OS X Yosemite became available, I quickly decided to update my hardware to it. After having many problems with installation (it installing to halfway and holding there for two-and-a-half days) and on the phone to Apple Support, my software had been downloaded and was working fine.

Since then (about the past four days), I have struggled to boot the Air on normal mode. As the progress bar goes through, it usually gets to about a quarter of the way through before freezing and refusing to budge, or halfway through, and doing the same thing. I'm having to resort to shutting it down manually and rebooting it in safe mode just to be able to turn it on.

I've tried Opt+Cmd+R+P and held for two cycles but it doesn't appear to have worked; it still gets stuck on the progress bar.

Is there a solution that I can do to solve this, or should I go to Apple and see what they can do?

Thanks.