It's a metabolism thing dude, the alcohol raises your metabolism so you spend more energy than normal for many hours after the intake, it also dehidrates you and keeps you in a water deprived state and makes you pee a lot more than you need too due to the cells trying to get rid of all the extra glucose in the alcohol, yes, alcohol gets metabolized inside you into sugar and that translates into more runs to the WC to pee.
You are now running on a slower metabilism and can't get rid of extra calories ( the ones being burned by alcohol induced raised metabolism ) as easily.
Drink gallons of water spaced out through the day, everyday, that will help get rid of toxins in your liver and kidneys and clean you right up. The more water you drink the more you will NOT retain because the body adapts to constant water influx and stops
thinking its going to run out of water. Same goes for food, if you eat LESS but you eat MORE TIMES A DAY the body forgets about the possibility of starvation which is what causes people to gain fat ( fat are energy reserves for when the cavemen can't find food and must survive on those stores ).
Continue added water intake, add cardio about 1 hour day 3 times week.