Weight gain AFTER the pill?

Sophia
Ladies, help! I went off the pill a month ago after being on it for about 15 years. Since then, I've been rapidly gaining weight. I am very healthy/active and have not changed my nutrition/workout regime at all except for significantly cutting down on alcohol. I also take a multivitamin, omega 3, a probiotic and Vitex daily. Has anyone else experienced this? If so, what did you do to correct it? 
Thanks, everyone!!!