The thing about a lifetime of eating unhealthily is that your brain is now primed to it, so making healthy choices may not come easily.
This doesn't mean you can change your habits - you absolutely can - but it's important to recognise that for a while it's going to be weird, feel hard and you will always need a measure of discipline.
Understanding habit formation & neuroplasticity is key, I think. There's a great book called The Source by Tara Swart which you should check out.
Start small - manageable baby steps.
Consistency is key.
You will "fall off the wagon", probably more than once. That's OK- just get back on.
Mess up one day? Fine. Do better tomorrow.
Having a bad week or even month? OK, but you've already made progress so just start again, you'll still be in a better position than if you give up.
If you only manage 1 day out of 7 of better habits, that's still 1 day more than you're doing now so don't beat yourself up, just carry on
If you use a handwritten diary, buy some stickers and put a sticker on every day in which you improve or maintain healthier habits. When you look back, you'll be able to see at a glance how you're improving and if you fall down, you'll be better able to identify why and remind yourself of how well you were doing before.
Use bright sparkly stickers or whatever- red, yellow, green could be good for highlighting improved habits, maintained habits or old habits.
We're more likely to build habits that stick when we can see progress.
If I were you, I'd start by reducing my portion sizes of unhealthy foods at mealtimes and supplementing with the same as husband & daughter. That way you're still getting the immediate dopamine hit while introducing healthy choices regularly. Over time, reduce the unhealthy portion in favour of the healthy portion and start swapping out old unhealthy meals for full healthy ones.
If you take 3 sugars in your tea/coffee reduce them by a teaspoon or even half a teaspoon at a time.
It will take time for your tastebuds to adjust, but they will. As a young teen, I hated salad - seriously it made me miserable - but one 3 week holiday with family friends where salad was served daily & I was too polite to refuse it, and by the time I got home I was converted 😆
If there's an emotional aspect to your dietary choices, which im guessing there is, get used to noticing and identifying your feelings and how you manage them. This will help you to replace unhealthy management behaviour with better choices. Journaling could help here.
Also a therapist - it's going to be tough and people who are very overweight tend to have lots of psychological factors tied in with their weight.
Rather than thinking of shameful vs virtuous behaviour - think about nourishing yourself. When you make a healthier food choice, you nourish your body and your mind. You also secure your daughter's wellbeing.
But, it's important to really teach yourself that you are worth nourishing and deserve to be healthy. You are not disgusting and you're not worth less than others.
It's going be tough because you need to reteain your brain and tastebuds, build new neural pathways and be kind to yourself when you don't do as well as you think you should.
Everyone messes up when forming new habits!
Nothing worth doing is easy, but the rewards for making changes are massive. You've got this- I believe in you :)