I was in the same boat you are. I drank 3-4 caffeinated sodas a day and never had trouble sleeping. I just decided to quit cold turkey one day, and after 2-3 days of intense caffeine headaches, they finally went away. You could either do the 'withdrawl' thing over the weekend or take an ibuprofen (something with less caffeine than the soda) to ease it down a bit.