Is this after the beach has been rinsed off?
I always found that the bleach hurt while it was on, but I kind of took it as a given with a full head bleach...
Maybe you mixed it up wrong? If you've used the product regularly in the past, I can't see it causing any problems now, other than if it was stronger this time. Did you leave it on for longer than normal?
Worst case senario is that you've developed an intollerance to the ingredients over time, but hopefully it's not the case...