'How do I break this habit?' Listener question

I am caught between wanting to change (lose weight, get fitter, move more) & being stuck not making those changes.  I have plans to exercise & eat well every day, but rarely do. This has been an issue most of my life. Even thinking about it now brings tension & conflict feelings. I feel like I'm fighting myself. 

The one obstacle/habit is the pull to 'not move'. This started as a young teen when I moved away from family & friends & it was safer to keep my head down & not move/be quiet for hours each day (before then I was active & outside most of the time). I ended up sitting & thinking  thinking, thinking, which eventually led to eating. Over the years I have found myself sitting & mindlessly thinking, eating for hours (& sometimes rocking back & forth) wasting days. 

My husband would work on a Saturday & I would mean to do so much with my day, but I would end up sitting, thinking & eating & then rushing to tidy up/ shower before he got home. I would then lie about my day's activities. The inevitable weight gain killed my marriage & I am now doing the same in my current relationship. 

There is real fear about this relationship ending & being alone, but there is also sadness/anger about not being loved unless I'm this different active slim person.

What is going on with me & how do I break this habit (I am now in my 50s)?