I have been underweight, healthy weight, and obese.
I can tell you that being slimmer does not automatically make you happier at all.
Just don't go thinking "if I'm this size, I'll be happy" because you just won't be. Eat well, do physical activity that you love, try new things and get help for destructive eating habits and you'll feel happier, REGARDLESS of size.
But i am obese and very very happy.
Why?
Yes i am insecure about how i look, no i dont like the way my belly is,
But I gained all that weight from life saving medication and my illness, but now?
I'm happier than I've ever been. Because i realise that I'm much healthier now, I have a job now, I am not stuck in the house now, I have freedom, AND I got a second chance at life.
I would be upset if someone judged me as "fat/lazy/disgusting" for that, so why would I hate myself for it??