Go to the drugstore and ask the pharmacist for Gel-Kam. It has a high concentrate of flouride & will help revitalize your teeth & help take away the pain and sensitivity. Put the Gel-Kam in both of your trays, and wear it/them for 4 minutes before you bleach your teeth, then do the same again for another 4 minutes after bleaching your teeth.
Is it just your teeth that hurt, or are your gums red/hurt from the bleach?
If you haven't given up on bleaching your teeth, when you do bleach them, put some Vaseline Intensive Care For Lips on your gums when bleaching...I know it sounds weird, but it will keep the bleach gel off of your gums.
I hope this helps!