11 hours after getting Brite Smile, the pain in my teeth is unbearable. Is there anything I can do?

It is a standart sitatuation that you have some pain but i am sure the result will worth it.
Within 24-48 hours your pain should go lower and you should get the result.
Advil may be a solution to relieve the pain.
I hope you will get better soon.

My wife states this each time she wears uncomfortable shoes that look great...
Most sensitivity from bleaching comes from dehydration of the teeth. Many people are not affected (most teeth whitening patients report zero discomfort), but some ARE and it can be very painful. Normally, within 24-48 hours the teeth rehydrate and all is back to normal, but with whiter teeth.
Most treatment is palliative, meaning just treating symptoms. The "cure" really is just time...
I am not a great fan of BriteSmile, as I think the results are hit and miss. The pain may not be worth the result. I think other methods, especially "Deep Bleaching®" or "KoR® Whitening" has great results and would be worth the pain.

I would take ibuprofen to relieve the discomfort as well as use the high fluoride toothpaste. I give my patients this paste a week before to avoid these side effects and prefer the ZOOM procedure. Brite Smile has too much heat involved. If your symptoms persist more than 2 days, see your dentist. Also drink and eat everything with moderate temperature.