Marching towards Onederland

I won't deny that I've been battling my weight almost my entire life. I have been fat and I have been thin and somewhere in between. For the last several years, I've been living on what I call the fat side. Its not fun, especially when one loves to shop for clothes. The selections are not exactly, um awe inspiring. I don't like loud colors or garish prints, and that's what the powers that be feel that the fat chick wants to wear.
I am not losing weight because I want to fit into nicer looking clothes, especially ones that do not contain an elastic waist band. My main reason is to improve my health. I know that when I eat healthy-not a radical diet, just a lot more fruits and vegetables and a lot less soda-I feel better. I know that when I work out, I feel good. Its all about the pleasure principle for me. I want to look good and feel good, and to do so, well its a no brainer.
Off and on for most of my adult life, I have dealt with working out and not working out. I swing hot and cold. The sad thing is the fact that I will work out on a regular basis, and then one day I'll wake up and just decide not to. No real reason, I just probably didn't feel like it that particular day. The problem is, rather than just picking up the day after, I just stop. And then I feel guilty and beat myself up to no end. And then, it continues and I don't work out, and the weight comes back on. Then more self abuse. Its a cycle, and I keep saying that I want to break it.
The bottom line is the fact that I have so much self loathing. I don't know where it comes from. Its not like I've lived a miserable life. I've actually had it pretty good compared to most people. But, still the self loathing is still there. So for me, its now all about getting my groove on and getting on with life. The bottom line is why do I have such a negative self view? Is it because I have this guilt that I have not lived up to other's expectations? How do I reconcile this? Ane what does it have to do with my weight?