I'm so glad you came to me with your alcoholic conundrum.
There are many factors that figure in to how booze hits you. Food, environment, previous mental state, etc. There are also lots of websites that will tell you the effects of alcohol and why, but most of these will scare you into never wanting to have a drink again.
Suffice it to say you've entered yet another phase of your drinking life. The one where you can kill a fifth of gin with a buddy and not really get wasted. Bravo, sir. Bravo.