Can you really trust your scales?

I have an ongoing battle with my self esteem. And it mostly stems from never being as thin or pretty or successful as my sister. The pretty is entirely subjective. Personally I will never see it. Someone calls me beautiful and I'll laugh it off as bias. It's sad but true. As is the successful I guess. She feels like a failure but I envy her life. 
My main issue is my body. I'm a curvy size 14. I haven't always been. Once I was pushing the scales at a number I'm not proud of. I've had fluctuations; gains, so-called 'heartbreak starvation', my graph is all over the place. But I am where I am now. And today, I'm not doing so badly.
I've been upset at numbers lately, but I'm not actually getting any continuity on my scales at home. They tell me I'm heavier than I am *phew*. The numbers change drastically every few days and that's not right. So, I measured myself at the gym. I'm a whole half stone lighter than I thought. And this is a comfort. My clothes aren't tight (except some across the boobs, but that's just something I have to deal with). So screw the scales. I'm going by how I feel. Because you can obsess over numbers and it can make you fucking miserable. I speak from experience!

Getting this out of my system

I've been away. I kept meaning to write. But I got very distracted. 2 months later I'm back with my tail between my legs.
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I've put on weight.

Yes I weighed myself tonight (worst time of day to weigh yourself, and worst time of the month too) but the numbers upset me. I'm sure there are perfectly good reasons for the numbers - time of day, just gone on the pill (notorious for weight gain), my boobs are growing (another charming side effect of the pill), I've actually been eating real, regular meals, I've had a week off work, I've drunk more as I've been celebrating...ENOUGH WITH THE EXCUSES!!!!

I have a new job that I start in 2 weeks. I'm moving to a new city. I have a boyfriend who loves me. All this good stuff is happening yet I'm still feeling terribly unhappy right now.
And it all boils down to this. I'm not worth it. I'm not worth loving. I'm not worth caring about or appreciating. I want to stop eating and run myself to oblivion on the treadmill. Maybe if I'm thin then I'll look at myself and think that I'm worth it. That I'm good enough.

As you can probably guess I'm feeling very low right now. I'm not feeling sorry for myself. I just genuinely hate myself and need to stop. Because its self destructive and will push away the people I care about. But I can't.