Start exercising. That's what got me straight. I was a good 100lbs overweight and a heavy drinker. I'd quit for a few months but always go back. It changed when I started exercising. Do as much as you can for 30 mins and call it a day. Work up a sweat and get out of breath. You'll feel good about yourself and that good feeling will carry over to the next day, and then the next day, and so on.
Initially, I didn't just quit drinking - I cut back. But over the course of a year, I eventually just stopped needing to drink. Now, a few years later, I'm in great shape and have a refrigerator full of beer that I never even touch. And if it weren't for getting on that treadmill for the first time, despite how much I wanted to just put it off and drink, I never would have gotten here.
You can do it!