Good for you in giving up soda!
Or as we Michigan people refer to it as, "POP". I haven't had any soda in 5 months. I don't miss it or the extra weight it packs on over time. The headache will be gone within 4 or 5 days. It's a bummer while you have it, but it won't last forever. I love water now, my body craves it and needs it. Especially lemon water. I squeeze in about a tsp of fresh lemon juice in my water at least 3 times a day. I also put a lemon wedge in my water besides and just keep filling the same container with the lemon in it. It's a really refreshing drink and has MAJOR benefits.
Read this article on the benefits of drinking lemon water. It changed my life.
As an added twist, what I might do if I want to zest up my water a little is add a couple of oz of cranberry juice along with the lemon. It has a very refreshing, slightly sweet, slightly tart flavor and is a great pick me up! I don't do that very often, because of the staggering amount of sugar and calories that most cranberry and other fruit juices have in them. But everything in moderation.
Stay strong and avoid the pop, oops, I mean soda!