Motivation is the hardest mistress. She's fickle. I try associating my gyne with shame and pain. When I go to the refigerator to eat a bad food, I associate it with more pain. When I eat a burger/fries/coke, they no longer taste good to me. When I think about going to the beach, and taking off my shirt, I associate it with shame.
It sounds like you are attracted to hot women. Use this as a powerful motivator. Don't be shy, smile broadly and practice talking to them at the gym. Try talking slowly and deliberately as if your words were important. Keep a diet and fitness journal and write down not only what you did, but how you felt. Re-read what you wrote a few days later. When you do eat something bad, eat only a tiny bit, and then force yourself to wait for a long time before eating another mouthful. You'll tire of eating junk especially when the ladies start noticing you in the gym. Women hate men who oogle them in the gym. They just want to workout. Make sincere eye contact and be Mr. Friendly and Helpful. It will pay off, and keep you motivated.
Get some tight wife beaters, and wear them to boost your morale. When you manage to get through a couple of weeks of solid workouts, buy yourself some new clothing that looks flattering and enhances your new physique.
You do not have the strength to do this on your own. There are no non-believers in foxholes during wartime. You're in a battle too. Pray and ask for strength and power and determination.
Finally here's three things that really help me. You may think they're stupid. Who cares? They work.
1. Grunt like hell when you really lift. Work at it man! Get ripped! Draw down on your animal power. You're a warrior inside.
2. Find a power word to say while lifting or doing cardio. I started with no stamina at all. When I'm 1/3 of the way through a tough 5000 meter row, I say, "IRON". I imagine myself as soft iron, heavy and malleable, potentially strong. When 2/3 of the way through I say, "FORGED". I am in a furnace, and my iron is being tested, and metamorping into something new and harder and tougher. Finally in the final minutes of my row I say, "STEEL". I am razor sharp, a sword of power, strong and able to cut through my weakness.
You got to reach deep and make yourself go go go. The enemy is the SELF: the weak shadow side of us that is lazy, makes excuses, and wants the short term things that give immediate pleasure. You got to re-wire your brain to succeed.
GO FOR IT