You only get to use long-term gains if they were long term (you owned the coins for more than a year - and can prove it), and it was in the year you cashed out. If you are cashing out in 2014, it's income for 2014.

You don't get to use previous years allowances if you never received the money. However, if you did cash out last year you should have reported them already (or filed an extension), or amend your return to include them.

Your accountant will be able do all this for you. You need to just let him deal with it.