I think you should not beat around the bush.. You have a self control and disciplin problem. Cut out fast food and you will do the same thing any time you walk into the grocery store. Just quit like most smokers do, try doing it less and less each day until it is nonexistent. Only eat when your body tells you too, not because your mind wants you too. (When you feel the growling in your stomach)
Wendy's has some better options than most fast-food restaurants, but watch out for the add-ons! I recall getting a Wendy's salad one time along with a packet of dressing. It was a creamy dressing - and the fat and calorie content was about the same as a Big Mac! So - avoid the fries, have a small burger with mustard or ketchup (no mayo), salad with lite dressing, a baked potato with some chili on it - no butter/sour cream, - just make good choices, and study their nutrition guide.
I'm not an expert, but in my opinion, I quickly see 2 options:
(1) Try bringing more of a healthy lunch to work. Make sure its filling, so you dont feel the urge to eat more as you work around food. It is the convenience as to why you eat wendy's, and probably fast food in general. In summary, try to provide yourself with convenience of a healthier alternative. As long as its healthier than what you've been eating at your work, it's an improvement. Oh, and you can always try the healthier things on the menu rather than something else.
(2)Quit working at fast food. However, that would stop you from eating outside of work.
Im still a teen, and when it comes to eating at fast food restaurants, I'm guilty. With the relatively easy access to fast food, I think it will take discipline to stop eating it. Personally, I try to convince myself that I'm wasting too much money on fast food. I think this helped me psycologically.
I've come to realize that whenever I'm craving junk food, its when I'm really hungry and have nothing else to eat at that moment. So my resolution is to eat filling foods, more on the healthier side, before I leave the house.
There's my advice, good luck!