I am the Thorian, known as Species 37 to you people. I am an ancient sentient plant that is fifty thousand years old. My ability to hibernate for thousands of years makes my real age impossible to guess though you are welcome to try.
The Bungie Universe is not the place for this, the Flood forum is the right place.
I will, however, help you: It is possible that you just reached the daily EXP limit. Wait until 1am and then you should be able to start earning EXP again.
[Edited on 01.01.2013 2:56 PM PST]