Discoloration from teeth bleaching(10 pts)?!

I recently purchased an at-home teeth bleaching kit that uses Carbomide Peroxide. I tried it last night, using my invisiline retainers as trays. My retainers fit quite tightly, and pushed a lot of the gel out onto my gums. When I took them off this morning, my teeth looked cleaner, and a tiny bit whiter. But upon close examination, I noticed that on the very tips of my upper teeth, there are very white spots. Like discoloration. I really want to continue bleaching my teeth, what should I do? All advice/input is greatly appreciated. 10 pts best answer!