This is food addiction. In my opinion, it's probably the most difficult addiction to overcome, because you need food to survive. By comparison, drinking and smoking are easy to give up because "just don't do the thing" doesn't work here - you can't tell someone to simply stop eating anything. It's like if you had a drinking problem, started the 12-step program, but still had to take three shots of whiskey every day to survive. With cigarettes, you can just stop buying them and keeping them in your house - an easy way to deprive you of the object of your addiction. With food, you've got to go grocery shopping and interact with food on a regular basis, even in a professional setting (especially if you work in the food industry in some way!) aka you're probably always near food. The difficulty also compounds itself if you live with others (roommates, spouse, kids, etc.) that also makes bad food choices.
The fast food companies, and processed food industry in America specifically, design their foods to be chemically addicting without regards to individual health. Overcoming this takes a massive amount of willpower and determination. Even when you break the cycle of addiction, the cravings will follow you probably the rest of your life.
I started in September of last year, so I've been at it for six months. It's been incredibly tough - much more difficult than when I gave up drinking and smoking. As others have said, you have to stop going to fast food places - so examine the reasons (other than being addicted to the food, obviously) why you're going there to begin with. Is it convenience? Cost? Social pressure? Try to find non-fast-food alternatives that can meet some of those needs. For me, meal prepping helped out a bunch. It's lower cost, and I know from day to day exactly what I'll be eating that day (and everything is portioned). It's not quite as convenient, since it takes a couple of hours out of my weekend, but on the days I'm working it saves me a TON of time just grabbing the bentos when I leave, and I don't have to wait in the drive through line on my lunch break. When I get home for dinner, it's already made just gotta nuke it. Starting out is the absolute worst, but it does get easier. Lots of days, you will go to bed feeling absolutely hungry.
As time goes on (and you inevitably start feeling better), try introducing more veggies into your meals and also introducing some exercise. This will help with the cravings and with the weight loss. It should help you sleep better. These things will have a snowball effect where you can start feeling better and better, as well as have more energy throughout your day, and your mood will improve, so you can stop the sad-crying.
Good luck OP. If you need more advice or motivation when taking this on, feel free to PM me.