There are a lot of reasons your site doesn't convert.
#1 - The page load speed is too slow. Amazon did a study that found for every extra 0.1 seconds spent loading their pages, revenues decreased 1%. I think your site needs to be faster.
#2 - The checkout process is horrible (no offense) - Never get customers to register before they enter their details. Try to cut the checkout process down and ask for only the details you need. If you really, really, really want customers to register, then make them do it after they have filled in all of their details. You will still lose some people this way, but a lot more people will stay, because they have pyschologically committed to buying from you once they have entered their details. People hate to waste time and feel like they made a bad choice, so they are much more likely to comply with your instructions once you have got some form of committment.
#3 - It is hard to tell when you've successfully added something to your cart. There needs to be a little popup or something that confirms you added something to the cart. I know that you have something that appears above the main content of the page, but this does not stand out enough and I missed it the first time I click the order button, which lead to me clicking it again and then realising I had put too many in the cart.
#4 - No trust signals - There are no prominent "trust signals" on the page that instantly reassure me that the site is legit.
and many more....
Hopefully this helps,
I like to think I know what I'm talking about because I run a conversion rate optimisation and SEO business.
BTW: All of this is meant to be constructive criticism. Please don't take any of this personally. (always helps to say this from past experience)
Feel free to ask more questions,
Jack