I'm currently doing internal bleaching for my front tooth (it has been root canaled). My dentist placed the bleach agent for 6 days, but the results weren't satisfactory, so she replaced the agent with another one, and put it for another week. My appointment is after tomorrow, but just yesterday my tooth started aching me, even though it has been root canaled, which means that the nerve is dead, so there's not supposed to be any pain. When my dentist drilled a hole in my tooth it didn't hurt, but now it's hurting me, since yesterday. Is this weird or is it normal? Please help me, I really need help, because my appointment is after tomorrow, and I don't know what to do because it really hurts.
Are there any disadvantages when undergoing internal bleaching? What's the worst case scenario? And if I didn't like the results, can I still have the crown done, on my tooth?

Thank you.