The 4-5 day sober period is due to the alcohol induced chemical reactions in the brain subsiding and the brain starts wanting that alcohol fix again. Then we drink and of course can't just have one or two drinks, right?
I really didn't drink much in graduate school because of the school demands, but I made up for it once I completed school and started working.
Then I didn't gain sobriety until I was 40; why, because I was close to hitting a bottom which in my case was losing my family.
The fact that you are 26 and sense that you have a drinking problem is a big plus for you from the standpoint that you are pretty young. Good for you for asking the questions now.
Do you have access to any kind of counseling? If so, you may want to see about getting a chemical dependency evaluation to see where you are at.
Your last post contains a lot of questions that require some soul searching and probably support to find the answers. An AA meeting may be a good place to start.
Take care and by the way, this is a fantastic place for support and advice.
Dave