Weight

So, I've always been overweight. The closest I've gotten to being slim was in collage, before I screwed up my back, and when I was lifting weights. I was down to 260, and looked ok I guess. But since my back went out it seems as if my weight just keeps going up and up. I'm almost 340 right now, and I hate how I look. Yet I find that everytime I try and loose weight my mind and body work against me. Last week I decided that enough was enough, I was going to start going for walks and cut back on my food portions. Not change what I was eating, just eat less of it. That afternoon while I was out running errands I stopped by Burger King and had a quad stacker. I hadn't had fast food for almost 7 months before this. And it wasn't till after I ate, and was feeling overfull, that I literally yelled at myself "WHAT THE FUCK DID I JUST DO!" I hadn't even thought about it, just bought it and ate. It was like my mind said "Well, he wants to loose some weight so lets fuck with him". Other times I will plan to start walking more, go on hikes in the afternoon while I was up but before I need to start dinner for when my Angel gets home. So I walked one day. The next I didn't wake up till so late I didn't have time to go before I needed to start dinner. So the next day I set my alarm just in case... then SLEPT through the alarm.
It's not even a conscious thing that I could say is just me being lazy, it's like my mind shuts down when I think about needing to lose weight. I've wondered for years if my weight problem was some screwed up way of me punishing myself for past sins. It's like I look at some of the bad shit I've done, and in response I am slowly eating myself to death. Not that I've done a ton of evil, I'd like to think that I've caused far more smiles than tears, but it feels like the bad stands out far more than the good when I look back sometimes. From the hearts I've broke, to the times my hearts been broken, to friendships lost, chances failed, people I've physically hurt, promises broken... just so much that I think in some ways eating has been my way of hurting myself back.
Does this mean I should see a shrink? I sure hope not, don't think I'm that bad yet. But at the rate I'm going my blood pressure will eventually cause a heart attack, in fact before my Doc put me on meds for it she was amazed I hadn't already had one. She's told me that several of my medical problems, from blood pressure to bad cholesterol to some of my back pains, are a direct result of my weight.
What is it going to take for me to get it through this thick skull that I need to lower my weight...