You'll probably be okay (actually I don't know much about Food-Grade Hydrogen Peroxide, maybe someone else does) but if you're ever worried about something like this (the 3 drops sounds like a light dose) then drinking milk will neutralize it. The yogurt probably has the same effect.

Gena, I was like you..... thinking what the **** have I done when I drank a few drops of h202. My head felt sort of fuzzy and lightheaded for an hour or so. I felt like some kind of mad scientist doing crazy experiments, LOL. But for me it's been wonderful. I don't drink it every day - maybe once a week, and only 2 drops to start with, then three now I'm on 4 drops twice a week or so. I clean my teeth with 3% every day. My breathing is so much better now - hard to believe how much this stuff has helped me. I started using it just three months ago in January. I feel great. Keep with it, slowly, gradually. For me there was no need to rush it.