Over It took a while and a lot of getting better was by dealing with the trauma that had caused the anxiety and bdd in the first place. So in your case, from what you've said here, maybe some cbt and counselling around how your upbringing made you feel would help you. I did some online cbt and also mindfulness was very helpful.
Also realising that it was bdd and I wasn't actually a hideous monster was a huge step forward. So you've done that already. It's the start of feeling better.
I took beta blockers for the physical symptoms of anxiety. Don't know if that would be relevant to you but perhaps medication is something research yourself and to discuss if you decide to see your gp about how you're feeling.
I would give myself a very short time limit to look in a mirror. So just a check over to see if I had food up my face or whatever, no staring or studying myself from all angles. I had to be very strict with this. I avoided mirrors for the most part tbh.
I focused on things about my body that were about being kind to it rather than what it looked like. So nice smelling shower gels and body oil, using moisturisers to make my skin feel soft, deep conditioning masks for my hair. I think that helped me connect to my own body again so it felt less like the enemy. Also eating better, lots of veggies etc but no calorie counting. Cutting out refined sugar, all alcohol and all caffeine as they all triggered my worrying mind.
Doing activities where it really didn't matter wtf I looked like. Like walking in the countryside, up hills or gardening. There's something about fresh air and getting your hands dirty that calms the mind.
God no idea if any of that makes sense. It was a few years ago now.
Basically, cbt and mindfulness (also medication if appropriate), focusing on taking care of myself and my body rather than what I/it looked like, getting outside and away from people/social media/advertising etc. and some lifestyle changes to help the anxiety.
The books reccommended here look very good. I wish I'd known about those. The NHS and other places online have some good tips and info to help you. I found it helpful to know it wasn't just me and I hadn't completely cracked up. Sorry I can't be more help. I promise you you can feel happy and good about yourself.
You are good enough and you always have been. You're one step closer to being able to see that for yourself. 