I now have four self-published ebooks on Amazon, and my sales are still basically flatlining. I have tried bloggers, ad campaigns, Facebook, Twitter, review copies, a Reddit AMA, Kindle Countdown, Kindle Free Promotion, and now a Goodreads Giveaways.
This may be an entirely unhelpful suggestion, but it could be worth having a think about why those things haven't worked, rather than just saying you've tried them and you're now moving on to the next thing.
I'm curious particularly about the Facebook thing. I just jumped on yours and seen you haven't posted anything since February, and you've only for 47 people following you. Have you been strategic with your Facebooking, or just been posting stuff? I notice as well that you've got really quite minimal engagement - most posts don't have any likes or comments or anything. So that's clearly not going to drive much traffic.
From what I've read, the people who have success with Facebook use it as an advertising platform instead of trying to build an organic audience from the ground up. They advertise a free reader magnet, and gather that data for their newsletter and future launches. I think what you need to do is pick one thing that you've heard people have had success with, a really try and replicate what they've done to be successful. Having a FB page by itself isn't going to do anything.
I do not mean for this to sound like a pile on... it's just something that's been on my mind lately. Recently I read a blog post about an author who tried Facebook ads and then basically concluded that they were expensive and it didn't work. She had a lot of back end data to support her claim. It sounded like a pretty compelling argument against them... until I saw the ad. I'm hesitant to post whose ad it was, because that would be unfair. But suffice to say it was basically a generic stock photo, the name of the book, it's genre, and nothing else. No wonder it didn't work. And to use such a bad ad and then conclude that the platform didn't work is silly.
Anyway, sorry if I've been too harsh, but what I would do is interrogate why nothing has worked so far. Pick one thing and learn exactly what you need to do to make it work. Your books do have good reviews and I think the covers and cool, so you're already ahead of heaps of people.