Oh my. This is not looking good. No passphrase is, well... not good.
There is only one thing you can try. I'm assuming that you used the native encryption tools that came with your install. Do:
where "username" is replaced by your username. Type your old login passphrase (not the new one that you recently created) to reveal the mount passphrase. If you get your passphrase, make an offering to whichever computing gods you worship and write it down. If this doesn't return your passphrase, you are simply out of luck and it is impossible to recover your data.
Let's get this step out of the way first before proceeding to the next. You should look over this how-to, but everything is dependent on recovering your passphrase.