Hm, you're in a tough spot.
Is your domain a unique name, like "Moz," or is it a description of what you are, like "SEO Info"? I ask because it's possible that your brand name is really a competitive keyword that you're just not strong enough to compete for, which could explain why you don't rank for it.
Also, have you looked through your link profile since 2013? It's possible that you have been hit by a spam penalty again. Even if you haven't purchased more links, if someone hits you with some negative SEO or if you picked up a few low quality links without high quality links to balance things out, it's possible you've been hit again.