I'm gaining because I eat thousands of calories.
The reason I eat so much is because I enjoy food. I have become addicted to unhealthy foods. I did the same with soda, and have been soda-free for 6 months. I really think that by going cold turkey for 2 weeks followed by introducing healthy foods will be the best bet for me.
I also have very weird work hours. I'[m a full time grad student, and work a job 7 days a week from midnight to 4am, then Mon-Fri 8am-2:30pm. CRAZY hours.